We have a number of cats. Simba and Millie are best friends, groom each other and the whole bit, but I would refer to the other cats as dog tolerant, though when it's cold in the winter they will share body heat with Millie, comfort first after all!
For me besides the rest one of the positive things about Millie is the required mainanance. I have bipolar 1 disorder and cycle quite frequently though this has improved some recently. Point is, just like the imperative to care for my children kept me moving while they were growing up, taking care of Millie has also become an imperative. No matter how I'm feeling she must be fed, watered, let outside. Most important she needs my love and attention. Of course we have a household of other animals, three other adult members, a son that frequently visits us with his girlfriend, and Multiple other friends and acquantances of Sam and Jonah( my other two sons). It can become overwhelmingly hectic and exhausting. Millie constantly shadows me, and all that I need do for an instantaneous mini break is to look over my shoulder or down at my feet and see her little face looking up at me.
Dogs are definitely not for everyone though, because as you pointed out, they are a huge responsibility and not everyone wants to take it on. I for one don't know what I'd do if there weren't others willing to clean the cat boxes, yuck! If I lived alone, I would probably not have a cat, though one of our five has thoroughly attached herself to me and now I can't imagine being without her.