Instagram wasn't set up this way. If you install it on a new phone or open it in-browser, you aren't expected to give it a recovery key to get your DMs back. They did add e2ee for FB Messenger, and it was very clunky besides not being secure at all (6-digit numeric pin).

Because either you have:

1. An E2E system where the provider has de facto access to the encrypted data, or

2. You shift key management to the users and let them risk data loss.

Either way:

a. The provider can release an app version at any time that accesses the data on the client side, and

b. Most of your users cannot differentiate between E2EE and SSL/TLS, nor are they interested in doing so, nor they care about it.

i never even knew they had e2e available, so they cannot have been too serious about people opting in.

a shame that they now have to shut it off because people didn't use something they didn't know existed /s