Those of us who never had to buy them now have to for backward compatibility. That especially includes us iPhone people who are new to the party and have to buy both the newer standard and the older. There are a lot of iPhone people.

That's more of an Apple issue than a USB issue, imo.

For anyone, you have to carry double the number of cables. You might find a modern charger or you might find an older one.

I agree that's annoying. But again, once the transition started, C-C cables came with A-C adapters. Those still exist.

Are you asking why USB-C is more convenient? It’s smaller, it’s reversible, it carries more power, it has faster data …. How’s it not more convenient?

The size difference is minimal. If you're saying you can bring a C-C cable but not an A-C cable, I don't believe you. Reversible is just a matter of flipping it if it's wrong. USB-A still has up to 30 W. Do you really need fast charging in public outlets? Data is moot, since we're talking about charging and ideally even using non-data cables to avoid unintentional data transfer.