I don't believe the married men I have sex with are straight. They may feel pressured by families or the way they were raised, but if they are putting their dick in me they are not straight. Bi-sexual yes, but not straight. I have had long term sexual encounters with guys who are married/were married/have children etc. Those who I got to know well, I often ask. They tell me society's pressures made them marry early. Though maybe one of them wanted to have a "relationship" with them, the rest it was mainly about sex. That is not to say I didn't enjoy their company. They treated me with respect, and not one of them called me a "fag" or else they would have been out the door.
Yes they were tops, yes they liked head and wanted to top me, but still - a straight guy who wanted to cheat on his wife would go and find another woman, not come to my apartment and fuck me, a grown man. I am not a sub, I am not effeminate, I don't act like a woman or wear women's lingerie. I am just a guy who likes guys.
As times goes on, I think social norms will change, at least somewhat. Those guys who felt pressured or locked into relationships in the past will be replaced with men who are more confident in their sexuality and not fearful of the repercussions of what might happen if someone found out they were gay.
Times are changing....despite the political views in the US now.