Idk if this is just me or a scorpio thing (maybe both) but I find it's extremely rare that someone can reciprocate what I give to them in a friendship. I'm my friends' listening ear, supporter, vault of secrets, etc. Often I'm not given as much as I give. I don't ask for it nor do I really open up. When it becomes too much I have no problem cutting people off. So, if this is the case for most scorpios, I think that's why we have trouble keeping friends.