Every one I see is modified. Some are modified so much that nothing is stock anymore. Is there a reason why I should buy it stock first?

Some people just want a great .22. Mine is stock (except for a scope) and I wouldn't have it any other way.

Some people just want a great .22. Mine is stock (except for a scope) and I wouldn't have it any other way.

Cause...its cheap, reliable, easy to shoot and maintain, as well hold its value a long time.  One of the best most popular gun made

A 10/22 takedown is better than the stock 10/22 in my opinion.

Because it's probably the cheapest way to get the receiver and start modifying it!

Because next year will be the 50th anniversary of its debut and  Ruger has sold more than 5 million of them, so a lot of people are familiar with it and there's a healthy aftermarket. Because some people claim it is the most widely modified firearm after the AR-15. Because, unless you get the rare stock 10/22 that shoots accurately out of the box, you can learn to improve its performance gradually, spending less than you would to upgrade an AR. Or more, if you want to.    Because you will have the stock parts to reinstall on the gun when you realize that aftermarket part  that looked so cool in the magazine doesn't fit/work/make it better.  And because the stock ones are still relatively cheap.
 
 
 

Every one I see is modified. Some are modified so much that nothing is stock anymore. Is there a reason why I should buy it stock first?

One word: Availability.

Its for the thrill of the build.......

I know that every time I get into any hobby, I like it stock or bare so I can cut, chop and rebuild.....

Also cause when I buy it already done, there's always something on there that doesn't float my boat.....

The 10/22 has a cool factor to it.....it being such a small caliber that can be used for so much applications.....

Customizing and building it you're way kinda makes it more satisfying.....

I bought my wife a 10/22, then started watching you toob. Found out how to make it run smoother, more accurate, ect. Wife said no. I went out and bought one for myself.  I like to do the "bolt on" mods myself.

1.Scope
2.Ammo
3.
4.PROFIT!

1.Scope
2.Ammo
3.
4.PROFIT!

The stock SS Take Down version is great as well as the stock SS Carbine model... I've both.
A scope on a 10-22 doesn't make it a customized 10-22, a bull barrel or some other permanent modification that removes an original stock part defines it as a custom rifle.
I think what you're asking is along the lines of buying a pro-customized 10-22 vs. a Stock version by Ruger and the answer would be - buy what you're after. There are only advantages and disadvantages dependent upon the intended use of the rifle and it all comes down to what you intend on using it for.
If you're after a highly precise 10-22 you may opt for a customized model available through X, Y or Z company - that may mean you are then limited to the type of ammunition it works best with. So research and find as much information as is possible before buying a customized rifle and make sure it won't compromise your true intended use. Spending the extra money because it looks KOOL may mean you end up with a rifle that doesn't fit your needs, which you will then deem it a piece of crap, not Kool.

Since you're asking such a question - YOU are better off buying a stock 10-22 and I'll assume you're in Hawaii, so I would recommend a Stainless Steel model and I would still highly recommend keeping the rifle clean and oiled after each use or handling. If you want a scope, laser, light, etc. then do your research and buy those that most appeal to you. 

If you find it on sale a stock 10/22 is the cost of the receiver, bolt and trigger group.

I bought 2, 1 to modify and 1 to leave stock ( except the stock which I changed to a folder )

Then you can build it to your personal taste. 
They can get ridiculous though. Buy a $200 gun and eventually build a $1000   .22.   Oh, but it's fun.

Yeah, depends where you want to go with it. Like MDS says, if you want accuracy, you can spend the bucks on one of the non-Ruger custom 10/22s. Or go straight to a CZ bolt action.

If you want something for plinking and teaching shooting basics to kids, buy a box-stock 10/22 and enjoy. You can start shooting at relatively low cost, then upgrade over time as your wallet allows.

The OEM stock on my 10/22 (20 yrs ago)  did not fit me.  Have tried three aftermarket stocks since. If you decide to put an adjustable stock on it, you'll find more that will fit a standard profile barrel than a bull barrel. 

A bull barrel will be generally more accurate. But you can get decent  accuracy from an aftermarket, standard profile barrel. A better trigger group will help accuracy. Those two items alone can cost more than you'll pay initially for the rifle. But like Hound  says, it's fun.

There's much more you can do. All it takes is money .

It punches holes in targets at a reasonable distance, probably won't fall apart right away, and you can let other people use it without being all paranoid about it getting messed up.

cheaper, less abused, you end up with what you want and not what someone else wanted and abused!

I picked this up. Not quite stock but close enough. This fit my daughter much better because of the adjustable stock. It's also foldable too.

Nice start!

For me, its hard to get "ONE" rifle with so much different customizing variations and accessories.....

I end up buying another of the same and building it a totally different way......