When we look at the reputation that PayPal has, very few other options even come close. Using PayPal means using the largest provider online, which means that you are also quite protected against losing your funds.
The drawback to PayPal is that you can only use it in licensed casinos, and then only in the jurisdictions where they are licensed. That means for example for a UK gambler to play at a UK casino, it would be possible to use PayPal. This limits the number of options for Canadian players who want to use PayPal.
The bottom line
Even though setting up an account can take some time, you can easily and quickly deposit and withdraw funds into your PayPal account. Making this the preferred option for those able to use it.