I'm not a parent so don’t take what i say personal. I had to take care of my little cousin from 1yr to 9. So if I had to guess what CONs would be from my experience with my cousin I would say all the cons are most likely emotional. I think the biggest consequence is that you don't get to watch someone grow up and share their life with them.
Watching and helping my cousin grow filled me with a sense of pride that I never thought about.
Depending on your beliefs not putting another good person into the world could be a con.
Helping someone else teaches you a lot about yourself. If you don't have kids you have no one can give your stuff to when you die and depending on your family no one is there with you when you go.
Also you will find it a lot harder to relate to the majority of your peers who become parents. Their lives will change very quickly and be focused 100% on their children.
They will understanably no longer be available to hang out or go on trips, their budgets will be constrained (they can't justify buying that new videogame, when they could buy school clothes).
When they do want to meet up or hang out they'll prefer to do it with other families, makes sense, childcare is easier in groups. They will also be going home a lot earlier, no more late nights, they have kids to look after.
Also i've found my friends who've become parents, also grow up a lot themselves. They have to be more mature and motivated. They have a family depending on them now.
What are the consequences of NOT having kids?