They don't make 'em for all models of firearms, especially revolvers.
I'm sure there are some guns without the option, but I've seen tritium sights for Ruger and S&W revolvers (I actually have a S&W with a tritium insert in the front sight). Likewise, tritium sights are available for Glock, S&W, Kahr, Ruger, Springfield, and several other brands of semiautos so in the end its not hard to find a gun that comes with tritium sights from the factory or for which aftermarket tritium sights are available.
Mine were glowing for 6 hours off that 2 second charge I gave them. 6 hourse gets me through most of the night and that is if I don't mount a small light inside my drawer to keep em charged when the drawer is closed.
Maybe, as others have suggested, it might be workable as a night stand gun (although to my mind the need to buy and install a special UV light to keep them charged kind of off sets the "saving money" aspect).
As a carry weapon, even 6 hours does not seem good enough for me. If I'm carrying, I put my gun on when I get dressed in the morning and it will then spend the whole day in the dark, either under a cover garment or in a pocket. By the time it gets dark enough to need night sights, much more than 6 hours will have passed. If I have to remember to give my gun periodic "recharges" to keep the night sights usable, I can guarantee I'll forget to do it sometimes (probably the one time I need it).
Its great if the system works for you. I guess I just have a reluctance to try and cut corners on a weapon I may need to bet my life on.