Why do other male dogs fancy DDog???

[Lara2]

DDog is about 11 years old (unsure of exact age - re homed) and neutered. In the last year other male dogs have found him very attractive - really sniffing at his bits (what remains anyway!) and sometimes trying to hump him. It wasn't always like this - other dogs used to do the normal sniff and be done with it routine.
So does anyone know why???

My dog was getting rather a lot of attention. Turned out she had a urine infection get checked just in case.

I believe it's because they're neutered. They don't give out the testosterone that an entire male would give out, so the other male isn't sure whether they're female or not, and have a go anyway!

Sometimes it's because their anal glands need emptying- makes them smell different

My dog normally never rolls in stuff but the other day did a short roll in something obviously smelly - for the next couples of days other dogs found him supremely attractive and virtually every dog we met jumped on him - he was