It's equally easy for both. But people using broswers only do it a few times, while bots need to do it many times. A second for a human every X pages is not much, but it's a death-knell for the general practice of bots (and they can't store the cookies because you can rate-limit them that way).

Imagine scrapping thousands of page, but with a X>1 second wait for each. There wouldn't be a need to use such solution if crawlers were rate-limiting themselves, but they don't.