These two are never gonna give us sweet dick-all. ONLY Bruce can lay down a note of note. Mike is as musical as a 2-note sax. And while Bruce likes to reminisce...poor, stupid, locked in the early 60s, addle-brained Mike only has lecherous lyrics to contribute. [See the album TWGMTR] The dullest bulb on any tree is NOT the guy you want to put your Grammy Award-winning name beside. It totally fucks up the resume.
Paycheques are one thing. But you don't pile 'merde' on your own hard fought for legacy.
Ever notice that absolutely NO ONE else wants to...or ever wanted to...write sweet-sh*t-all with the love-boat? I have.

What a clown's ass!!!
I'm pretty sure if Bruce didn't want to be connected to Mike in any professional/reputation capacity, he wouldn't go on and on in interviews about how Mike is as much of a genius as Brian is, as if Brian would have been just as likely to be pumping gas if Mike hadn't saved Brian's songs.
Bruce has pretty much *never* since rejoining the BBs in 1978 shown any particular desire to write or sing much of anything, either within the BBs or outside as a solo artist. If you went to a BB show in the 80s or 90s, you may have not heard a single Bruce lead during the show. He sang around 2-3 leads (depending on how you want to count them) spread across the six "proper" studio albums released after rejoining in 1978 (half of "Endless Harmony", half of "She Believes in Love Again", a little bit of "Somewhere Near Japan", two halfs of songs on SIP, and a few other bits perhaps).
His writing has been slightly more prominent but not by much. "Endless Harmony", "She Believes...", a 1/4 co-write on "Somewhere Near Japan", a half-cover/half-original on the SIP album, plus the "Happy Endings" single. Maybe a thing here and there I'm not remembering.
Bruce is clearly a solid musician/keyboardist (although we haven't heard him do much of anything even in that realm in EONS). He just seems to have zero drive to sing many leads or do much of any writing, let alone releasing his own music. I think when he rejoined the BBs in the late 70s, this aspect seemed like a case of being humble. I think now it seems much more like he doesn't give a f**k and digs the perks (chicks, paycheck, fame) of being in Mike's band.