It is natural to want love. It is natural to like someone who's physically attractive and shares a lot of interests, but sometimes it's better to be single and alone than to be with someone who is not emotionally available and makes you feel unappreciated. Dating someone on the rebound will do that and here's why you shouldn't do it.
1. It's on a bad foundation.
Kinda speaks for itself, but let's face it, the person on the rebound is dating just to get over their ex. You want someone who's on a clean slate, not someone hung up on their ex. There's lots of factors that make it bad. For example, I dated a girl who just got out of a 5 year relationship and her ex moved out of her place the week of our first date. Sure she didn't complain about her ex but she sure as hell wasn't over them. I found out late, but pursued because I was blinded by the fact we had a lot in common and she was really cute.
2. It gives you false hope.
Sure, there are no guarantees in dating even if a person isn't on the rebound, but the further you move with someone on the rebound, it makes you think you're getting a real relationship, but you're more than likely just a stepping stone back to their ex or someone they think is better. The more you see them, the more likely it is you'll get attached and once it ends, it bites you in the ass.
3. You feel like you're walking on eggshells the whole time.
While relationships do take time to develop, with rebounders, you basically gotta go at a way slower pace than you naturally would with someone who isn't on the rebound. They have a tendency to act super hot and cold and they could perceive you showing just a tad interest as being overly interested and then back off for a little bit or end it all right there. Again, there are no guarantees in dating, but as soon as they act cold back and forth, you feel like you gotta be careful about everything you say and do or else it'll be over right away, which it probably will be sooner or later.
4. They don't last (for the most part)
There are some rules to the exception where people get into a relationship right after ending one and they last for a long time, but it's highly unlikely. Longest one I've had where the girl was on the rebound lasted 2 months. Even for the short amount of time you date, it can screw you up for awhile.
5. It shatter your self esteem and confidence
So that relationship or fling you had made you feel on top of the world. That person could be everything you wanted or you feel like you have found the one. That's not to say they're perfect or put them on a pedestal. You shouldn't do that regardless, but from my experience, the two women I've been a rebound to were actually women I had a ton in common with where it was hard to walk away from. Once it ended, it made me think that I couldn't even make it work with a woman who had a lot in common and screwed up my perceptions of dating. Don't get me wrong, having physical attraction and a few things in common are important, but you never let it get in the way of red flags. Ignoring red flags or putting up with them will eventually cost you. It can also hurt your self esteem confidence to keep you from getting another girl or guy for that matter.
6. Before you know it, you're on the rebound.
I can't speak for everyone else who's been used as a rebound, but from my experience being used as a rebound both times has put me in a spot where I was using other women to get over the one who rebounded on me and it is fucking awful. I mean I'm sure it's not fun to be on the rebound, but it's even worse when you're rebounding from being someone's rebound. Someone on the rebound can get back with the ex. You can't exactly go back to someone who you were just a rebound to. Once they've used you, they're most likely done with you and they make you feel guilty and now you're there to pick up the pieces. After I get ditched by the rebounder, I would date and hook up with others. It would be a slight distraction from the pain of being rebounded, but if it didn't work out then I'd be back to being completely miserable.
Overall, these are my reasons for not dating someone on the rebound. It can mess you up for a long time and you deserve better than to be someone's emotional crutch, sex object, or second best. If you do find out someone you're seeing or you like is newly single or hung up on the ex, it's best to leave it, let them figure their shit out, and maybe get back to you once they're ready.
It's one thing if you're just looking for sex and they are too, but a lot of times, you can't help who you like and develop feelings for and you deserve better than someone who doesn't know what they want. They're most likely looking for an emotional crutch or a bunch of people to sleep with.