Yep. Certainly clients can create their own custom experience and allow users to have options/choices on how to handle interactions. The published event content should be agnostic.

Like open url in an internal app web browser, open a different app. Or a podcast event with a mini-player, vs a dedicated (Nostr supported) podcast app. Same as select a preferred Lightning wallet.

The only real incentive to use custom is lead-gen or bring new people to your client app - but again, it’s a self-serving approach and not for the greater good.