Oh, there are a lot of people who, because of various sorts of problems, learn to self-cath. If I were doing the kind of deco diving with several-hour-long hangs, I might consider it (with an appropriately designed one-way valve to prevent backwash!). I can't wrap my brain around spending a couple of hours in a wet diaper, myself.
Good thing I have no intentions, now or in the future, to do dives with multiple-hour deco!
I will offer one idea for making long dives more comfortable, though: Salt. A handful of salty snacks a few minutes before getting in the water will reduce urine output and keep you comfortable longer.