We used to have a version of ArrayList that bundled an allocator in the stdlib, we removed it because our experience having written Zig code for a few years led us to reach for the allocator-less variant almost always.

One aspect your argument is missing is that if you are juggling many ArrayLists, having each bundle its own copy of the allocator (instead of storing it just once) means wasting 16 bytes per ArrayList. The allocator-less variant is simply more flexible in that regard.