Can’t believe “calendar” wasn’t mentioned. IOW, scheduling.
Yes, minicomputers have a lot of great uses.
But they will never replace a straight-forward telephone. I want more pay phones back. When it gets lost or dies, one should always be able to fall back on something. Never mind power failures. Although Verizon FIOS has ruined the utility of our corded landline by failing during power out. Curse them.
And for calculator? Only if you download the TI graphing calculator does it come close to the scientific type. Common calcs? Sure. But not sophisticated calcs.
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“TI” is algebraic.
Too many strokes to operate; RPN rules.
I've never had a power outage that outlasted the battery for the FIOS system. I do find I need to replace the batteries every 5 years or so.
If you have long outages, maybe you ought to keep a spare or two on hand. Or disconnect the battery except when you need to use the phone so that it doesn't drain. (I do buy my batteries at the local Battery Plus instead of from the phone company. Cheaper, although there are even cheaper options online. And I just leave the old one with them- no concerns about disposal.