"Every person who has ever held a check -- ANY CHECK -- from you in their hands, regardless of what is written on it, can debit your account at will. Every waiter, every grocery store clerk, every person involved in the processing chain."
And what's to stop every person who has ever held your Credit Card from doing the same? Thankfully many institutions are now asking for a zip code when you use a credit card online but most still don't and that means every waiter, grocery store clerk, etc... who has held your credit card long enough to write down the number could use it to go on a shopping spree.
This varies by country, but in the USA by law your maximum possible financial loss from this is $50. The credit card issuer is liable, and that is why they put energy into fraud detection systems.
By contrast the immediate damage to you from misuse of your check information is much worse.
And what's to stop every person who has ever held your Credit Card from doing the same? Thankfully many institutions are now asking for a zip code when you use a credit card online but most still don't and that means every waiter, grocery store clerk, etc... who has held your credit card long enough to write down the number could use it to go on a shopping spree.