You're right that bank account numbers in the US are insecure, but you're wrong that this is why checks are popular here.
Checks are actually the source of the problem. If you have access to blank check stock and MICR laser toner (both readily available on Amazon, since business accounting departments will routinely print their own checks for payroll / bills), you can make seemingly valid checks to withdraw funds from any account number. This is still a problem.
The reason why checks are popular is because until recently there hasn't been a cheap + accessible + official + unencumbered way to do electronic transfers between personal accounts. The infrastructure existed (ACH), but only businesses could actually initiate deposits/withdrawals. Individuals could initiate full-service wire transfers, but those are risky (there's no way to reverse one done in error) and banks typically charge $25/transfer - which is far too expensive to use for anything routine.
PayPal came into existence so people could purchase goods online (on eBay, specifically) and have the option of performing a chargeback if the goods weren't delivered as advertised.
(Checks will probably still persist for some time, since all the online payment services want to charge percentage fees if they think you're acting as a business. The beauty of checks is that they just work and don't insist on taking a cut of the payment.)
Checks are actually the source of the problem. If you have access to blank check stock and MICR laser toner (both readily available on Amazon, since business accounting departments will routinely print their own checks for payroll / bills), you can make seemingly valid checks to withdraw funds from any account number. This is still a problem.
The reason why checks are popular is because until recently there hasn't been a cheap + accessible + official + unencumbered way to do electronic transfers between personal accounts. The infrastructure existed (ACH), but only businesses could actually initiate deposits/withdrawals. Individuals could initiate full-service wire transfers, but those are risky (there's no way to reverse one done in error) and banks typically charge $25/transfer - which is far too expensive to use for anything routine.
PayPal came into existence so people could purchase goods online (on eBay, specifically) and have the option of performing a chargeback if the goods weren't delivered as advertised.
(Checks will probably still persist for some time, since all the online payment services want to charge percentage fees if they think you're acting as a business. The beauty of checks is that they just work and don't insist on taking a cut of the payment.)