Why do paypal block accounts ?

Paypal blocks account mostly because you are violating there terms of services. Few of the most common reasons of Paypal blocking your account are -

1. Using multiple paypal accounts - Paypal only allows 2 accounts per person to have. One professional and other personal. Anything more than this, and you are in trouble
2. Filing wrong information - If your IP is not matching with the information that you have filled, than during regular checkup, paypal may block your account.
3. Suspicious Credit Card information - If you have used Virtual Credit Card or similar card and paypal feels that the information may not be true, they will block your account.

And even if everything is fine, still you never know, they can ask for you to submit your address info. So better follow there rules, if they are that important to you.