The guys in "straight" porn are better-looking now than several years ago as the industry responds to what audiences want. I did some porn direction/production in the 1990's, and we generally put the younger and/or better-looking guys in "gay" scenes because the main audience for "straight" porn was "straight" men, and they didn't want to feel inadequate by seeing a very muscled (or trim) guy with a huge cock.
Audiences are different today; more women watch "straight" porn and they want good-looking men. Also, there are a lot more men exploring same-sex attraction that are more comfortable watching "straight" porn than "gay" porn.
Note: I use quotation marks for "straight" and "gay" because those labels don't apply to models making porn: Lots of guys with very little attraction to other guys make "gay" porn, and many guys who would be considered "gay" by most definitions make "straight" porn. More than once I've had guys on set getting their dicks fluffed before a shoot by their boyfriend before fucking a girl–as well as the opposite.