Lifetime annotations can be burdensome when trying to avoid extraneous copies and they feel contagious (when you add a lifetime annotation to a frequently used type, it bubbles out to anything that uses that type unless you're willing to use unsafe to extend lifetimes). The solutions to this problem (tracking indices instead of references) lose a lot of benefits that the borrow checker provides.

The aliasing rules in Rust are also pretty strict. There are plenty of single-threaded programs where I want to be able to occasionally read a piece of information through an immutable reference, but that information can be modified by a different piece of code. This usually indicates a design issue in your program but sometimes you just want to throw together some code to solve an immediate problem. The extra friction from the borrow checker makes it less attractive to use Rust for these kinds of programs.