Exactly the same for me -- it's personal porn for me. Knowing she turns him on and making sure she is dressed to pleaseThis might sound strange(or may be not) but chatting about wife with another guy is definitely a big turn on. However for me it’s not just about fantasising other guy banging her but more about how intimate they can get.
Things like her going on a date with the guy, or even just for a coffee and him watching her, conversing with her, touching her, caring for her is kind of a turn on.
Probably, all these fantasies stem from the desire that I want to see her being more carefree and having more fun. Not sure if this makes sense or may be I am just deluded!