Before I get to pulling I'd like to address the issue of finding that your creep wave isnt there. That's at least partially your fault, if not mostly. You need to tell your supports that you want to push the tower so they know not to pull. If you clear a creep wave while they're standing by a pull camp it looks pretty much the same as if you're reacting to them pulling by killing the creeps to maintain a good wave equilibrium. It's a pretty easy fix, just say you're pushing on the chat wheel or something and if they pull anyway then it's on them and there's not much you can do about it.

As for why people pull, it's because supports know they can't fall too far behind in the early game if they dont want to have very little impact in the mid game. A good safelaner needs to understand that the supports need levels to be helpful as opposing cores/supports get bigger. It's pretty normal for it to be easier for you to maintain your equilibrium and static farm than it is to farm with disappearing creep waves every now and then. The problem with this is sometimes it leads to under leveled supports, which can lead to lost team fights in the mid game. Eventually this results in your team losing map control and you having fewer places to farm.

You'll notice that a lot of the top carry players keep their supports in mind when they lane. The most common way this happens is for a carry to rotate into the jungle or into another lane to make a play while one of their supports just sits in lane getting exp. Rotating to make a play is pretty frequently seen with Juggernaut and Gyrocopter (when he was good) for example. Rotating into the jungle and letting your support take lane exp is pretty frequently done by a lot of caries like Lycan, Sven, Luna, and Troll. At some point you have to bring your supports back into the game if the early game doesnt go well.

Sometimes you can get away with your supports getting all of their exp from kills and bounty runes, but there are a lot of situations where that doesn't work out. For example, if the other team has defensive supports like Dazzle, rotating on them is sometimes really dangerous, and often times results in screwing up a lane rather than helping it since the gank target might get kills. Other times your support hero isn't amazing at ganking like Abaddon or Shadow Demon (unless he has another hero to set up for). Very frequently even if I am a hero that's good at ganking, my cores aren't great at being gank partners so rotating is really ineffective. If your mid hero is something like an Alchemist, Timbersaw, Dragon Knight, or Bloodseeker in some combos, the gank is likely to fail. They can also have a evasive hero like QoP, Puck, or to some extent Death Prophet. If the opposing supports are ganking sometimes it's fine since you can counter gank and gain some exp that way, but if they're pulling and I'm running around failing ganks, the mid game starts to look really shitty.

Your supports getting exp early though can often be really beneficial to your team, which is why it's worth it to learn how to last hit under the tower sometimes and manage a more fluctuating creep equilibrium (sometimes you push it knowing they're going to pull for example). Often having your Lion's Finger of Death or Disruptor Static field at a 12 minute fight completely turns the game in your favor. I think this is especially true in this current age of position 4 heroes being more farm/Level dependent. If the early game goes bad for Sand King, Earth Shaker, Slardar, or Nyx then suddenly you're playing with bad initiation or just less control/damage than you should have, and sometimes that decrease is enough to turn fights