This is normal, if that helps.
True some toddlers don't do it, and it can feel like you're surrounded by those that don't (people spin the reality of sleep a lot) making it really hard.
It will get better, promise. Our DD woke regularly until around 18 months. She's not over two and does a lot less, although still does if over tired, or ill, or teething, or feeling wobbly.
Personally i think the 'habits' thing is rubbish. It maybe works for some children, but as you say, you can work on all the good 'habits' in the world, it won't necessarily stop them waking in the night.
Over tiredness and teething can both have a big impact. So can hunger - she has a fast metabolism so if she's not eaten well she'll wake early these days, until 18 months she would feed in the night and was hungry, despite all the books saying they don't 'need' to feed in the night past 6 months. But that's an arbitrary, average line. In the same way that some adults could go all day without eating and be ok, but i would be feeling wobbly, headachy, shaky if i did that.
Finally, as others have said, they are really little still. Often then are waking in the night for reassurance. We know they are safe in their rooms, but as animals they are programmed to seek comfort, reassurance and physical closeness from their parents to ensure they are safe at night for much longer than we might like.
some co sleeping (maybe part time?) might help. We have a doulbe bed in DD's room and one of us will often cuddle up in there with her if she needs support. It's not for everyone, but i'm interested in the shortest path to the most sleep for everyone, as well as giving her the reassurance at night that she needs.
Also lately family staying has meant we've had her cot in our room, and she's often slept well like that - she can sense she is not alone. Might be a better option if they are too wriggling in your actual bed.
As others have said, i have stopped worrying about the long term bad habits of this, too. No teenager sleeps in their parents bed, i assume DD will stop needing this when she's ready, and until then i opt for an easy life!