The reason why a lot of people use paypal is because it is so easy to use, for example if you want to make payment, you just need details like the other party 's email or moblie phone and press "continue" button within an short period of time, paypal will update the party's payment status by their mobile phone which mean they receive their payment faster. Paypal even allow you to pay in different currencies.
Secondly most auction and online shopping platform like eBay prefer paypal, 80% of eBay buyers are more likely to buy again if PayPal is offered while 5 out of 6 eBay buyers prefer paying with PayPal.So if you didn't like paypal, majority of the market is not going to give up paypal just because you cannot control your spending.
Finally nowsday local bank made it very troublesome to do internet banking online, like DBS and UOB, you must have an iB Secure "Token" Device to provide the secure number for you to log in, if you lost the token, you need to pay about another $20 to get an new one, otherwise you cannot perform any iB transaction : http://dbs.com.sg/personal/ibanking/newtoken
I stopped using paypal after my account was hacked. Now i just do the old fashion cc way.