I used to live in an area with lots of apartment buildings and had to babysit a friends dog for a couple of weeks. I met a couple of people when I took the dog out at 6:30am because they were doing the same thing. Ran into the same people every day. Plus you always let the dogs visit (sniff each other) so starting a conversation is almost automatic.

Now I have my own dogs. Easy to meet people if you go to obedience, agility, or other dog classes.

With a dog you get all of the above, plus the affection from the dog, plus the additional exercise.

Dogs are a pain in the ass. They smell bad, and make your home smell bad. They require constant attention. Leaving them at home, locked up, all day long while you're at work working long hours is cruel. Your apartment/condo will require you to pay a big fee to get their poop DNA tested, and when you don't pick up their poop, you'll be slapped with a huge fine. Honestly, it's easier having a child: at least children can go to the bathroom by themselves after a few years, and eventually can feed themselves too.

Dogs don't fit in with every lifestyle.

Not a great idea if you are out at work all day.