When i read someone talking about their "partner" I immediately think homosexuals, trying to whitewash things.
"Partner" has become code for "Lover." Either can apply to same or different gender couples.
"Lover" sounds tawdry and uncouth. "Partner" implies there's more than sex between them.
Nowadays, "partner" has become more acceptable than spouse, husband or wife for obvious reasons. Even among heterosexuals, the rate of marriage has declined while they cohabitate and raise families. "Partner" is more generic, so corporate, government and social America tend to use less specific terms to avoid offending.
That's my read on it, anyway.