The simple answer is that if you didn't cache, DNS traffic would skyrocket, and the load would pile up on the authoritative servers, which were intended to be small, and during the early days of the Internet, were frequently on bandwidth-constrained links.

DNS is designed to distribute query load to the edge as much as possible, and that's enabled by caching. It just so happens that "the edge" is now becoming concentrated among a small set of providers because they wanted to make a business out of it.[1] They knew that this would be expensive going in, though.

[1] Nobody has to use 8.8.8.8 or 1.1.1.1. Most people can use their ISP's cache or a local cache instead without any noticeable difference in behavior.

The problem is there is a noticable difference in behavior because the ISP cache is overloaded so queries take longer. Sure, that's not everyone's experience, but there's a reason people chose to use alternate servers.