As much as I despise GAFAMs, as a user I would still rely on a url shortening service from them over one from your for the same reason they are used: long term availability of the service. Despite expected enshittification or sudden discontinuation of services, they are much more capable of maintaining such a service on the long term than an individual (and I'm a happy self-hosting enthusiast myself).
Which leads us back to root42 (npub162r…ewqz) original stance: never use a url shortener!