Driving License	Passport	PASS Card
Lets you drive	Lets you travel abroad	Doesn't let you do anything special
Difficult to carry around	Easy to carry around	Easy to carry around
Must be a UK citizen	Must be allowed to drive	Just need to be a UK resident
First one costs £88.50	First one costs £34	First one costs £15
Renewing costs £88.50	Renewing costs £14	Renewing costs £12
Renew every 10 years	Renew every 10 years	Renew every 3 years

So, more people can get PASS cards than driving licenses. They're less useful, but in the same period of time a PASS card would cost you more.