I read on an article at Nerdwallet titled 5 Health Savings Account Rules You Need to Know (mirror):
Irvine warns that the majority of HSA administrators require the accountholder to have a steep minimum amount in their HSA before they can open up an investment account.
Why do the majority of HSA administrators require the accountholder to have a minimum amount in their HSA before they can open up an investment account? Isn't it in the best interests of the HSA administrators to offer an HSA account to their customers that is as flexible as possible (i.e., not having any such minimum)?