He knows why she's has no/low sex drive.
He knows she's trying to change things.
You are hilariously naive about why men who use prostitutes, use them.
From the horse's mouth, see it in UK punting.
"Don't want to fuck one woman for the rest of my life"
"I'm bored shagging the same person"
"I can have sex with women who I could never get in real life, hotter, younger, that's the whole point"
"I want to do stuff I wouldn't ask my wife to do/wouldn't want to do with my wife"
"I want to try out a black/Asian/Brazilian/thick/trans woman"
"Life is too short for sex with only one woman".
From the horse's mouth, hear it from prostitutes themselves.
"They show me photos of their beautiful girlfriends and wives, like they want to prove they can get women without paying, they dont say they never have sex, they say they are bored, the sparks gone.....they say it's their last time, always their last time .... They always turn up again".
Most men who use prostitutes have partners and most still have sex lives with those partners.
Educate yourself. Your advice is based on misinformation, on projecting women's values and feelings onto men, on naive assumptions about many men's attitudes and values around monogamy and relationships.