The best thing to possibly do is to get your own blockchain wallet because it is really popular and being used by a lot of people.
And if you put all your bitcoins on there you should be fine and save. So you can invest in it more and put it there.

I Think it will because if they see you can make millions without doing anything and just waiting for your bitcoins to go up then it will probably motivate them to also not give anything out and see for myself.

The difference is that with bitcoin you can't buy anything you want with it. Like you can't go in a restaurant and just buy some food with it. Maybe that will happen in the future witch is possible. You can buy anything with money.

They are holding it, because they know that bitcoin will rise in the future so they will maximize their profit by doing this. It is actually a smart thing to do if you don't need the money that you have stored in your wallet. Simply let it there. Don't spend it, because in the future it will surely rise.