it’s because american corporations put profit above all else, and someone probably crunched the numbers and determined that faster transactions make them more money despite higher occurrences of fraud

How could entering a 4 digit PIN be slower than "printing a piece of receipt, handing over a pen and waiting for the customer to sign"?

When still requested, the signature is often just scrawling something into a signature box on a touch screen of the same device with the chip reader or contactless receiver. There might be some stylus dangling on a tether and often a spastic finger tip is sufficient to satisfy the UI.

Generally (at least in my part of the US) people stopped being asked to sign for small purchases several years ago; usually now convenience stores and big box stores under a certain dollar amount just ask you to tap a button instead of sign.

This is the same with PIN in Europe (at least for contactless): Below a certain amount you do not have to enter the PIN.

Signing is very rare these days, non-existent for small purchases... and still seemingly rare for larger ones. I've spent hundreds of dollars in single transactions without signature or pin.