1. “It's too heavy” This is my favourite; the average dropper post weighs around 500 to 600 grams, and a lightweight seatpost weighs around 200grams. What? Your little chicken legs can't push an extra 300 to 400 grams up the hill?
2. “My bike doesn't come with one” Simple; sell your bike and buy a new bike. Most new All Mountain bikes come with dropper post, so buy a new bike.
3. “I don't need one, I can just put my seat up and down with my quick release” These people are classic, they are usually the same dickheads that don't bring water, or even have a spare tube when they go riding. If you ride with this type of person the only way you can get through to them is to not stop riding. Up, down, flat, don't stop for them. They'll get the idea eventually.
Three (good) reasons why you should get a Dropper Seatpost:
So picture this, you are riding a new track with your mate. He has ridden it once before, and he tells you he doesn't really remember it because it's a long track and they rode it a while back. The track is undulating and you can see he is using his dropper post a lot, he is putting his seat up and down all the time depending on the terrain. After a longish up, you see a down and you ask very annoyingly“Should I put my seat down now?”
Reason No. 1 why you should get a Dropper Seatpost.
Your friend doesn't like you. It is not up to them to think about your ride for you, it's going to be a long ride and you asking if you should put your seat up and down is going to get old. So you both continue to ride for a while longer; it's a fun track that is still undulating. Your friend hasn't used as much energy as you because they have been able to keep the flow and drop their seat on the downhills and then up on those fast flat sections after (also put it down again just because they wanted to do a sweet manual and a wall ride), and then carry more momentum through to the uphills.
Meanwhile you have been getting off your bike and manually putting your seat down for the downs, then leaving your seat down, so you can stand and grind across the flat sections, then sometimes on the uphills if they don't look too long. But then there is a long steep climb ahead. Your friend doesn't speed off, you just drop off... many minutes later you finally make it to the top.
Reason No. 2 why you should get a Dropper Seatpost.
Your friend is starting to hate you, not only do they have to think for you, they now have to wait for your tired arse. Then, as you swing your leg off your bike and start to drop your post you start saying “See, you don't really need one of those dropper seatposts, I have a perfectly good quick release.”
Reason No. 3 why you should get a Dropper Seatpost.
Your friend wants to murder you. They have been thinking for you, waiting for you and now you have the gall to say you don't need one! The scary part is, they are going to murder you! And they have worked out how they are going to do it. They are going to say in a casual manner “Don't worry about dropping your seat just yet, it's only a short down, and you'll just have to put it straight back up just around the corner.”
But they are lying, you should put it down because that corner they are talking about is really steep, sharp, rocky, rooty and as you go around it, your seat will hit you in the bum and flick you over the handlebars off a large cliff. And just in case you think you're a better rider than that, they would have ridden it first and be hidden around the corner with a stick in their hand, ready to put it in your front wheel. Then, at your funeral they will be distraught over the loss of their best mate. They are starting to think that killing you may have been a little over the top. Your partner will also be at your funeral and be distraught over your death. Over the following six months they will console each other and help each other through this tough time, until one day they will not only be dating, but will be living in the same house, the house that you used to own.
Shit, that all got out of control fast! If I were you and didn't have a dropper seatpost, I would be keeping my mate well away from my partner and talking them down any chance I get. Or, do yourself a favour and buy a dropper post; it could save your life.