it only confuses newcomers, as they think Bitcoin addresses expire and lose their validity
I have indeed seen questions about this a couple of times.
Before, the "receive" tab worked perfectly, you had an address that only changed if you actually received funds in it.
That's how the software of some hardware wallets behaves: you can't get a new address until the old one gets funded. It's terrible for privacy: I want to be able to give different addresses to different people, and if some of them never get funded, so be it.
Once expiration time has passed, Electrum will issue the address associated with that invoice to another invoice again if it's not yet used.
That's not good. Say I give an address to someone who wants to pay me $1, but doesn't pay. Next time, I give the address to someone who buys my second hand jet, and I receive $10 million. Now the guy who didn't pay me $1 knows I own $10 million. It may not be on-chain address reuse, but it's still address reuse.
IMO, it's more preferrable for newbies to use that tab so that they may be able to unintentionally prevent address-reuse.
Based on my example above, the opposite is true.