That's a bit like asking what did carpenters did with hammers and hand-saws in this age of CAD/CAM. :)

I assure you the Altairs were quite useful. Mostly, owners enjoyed the luxury of working on their very own computer, rather than a time-share machine's account from the corporation or university.

It's difficult to communicate how this felt, in this age of ubiquitous computing. A machine that one could reboot whenever you wanted. Tinker. Explore. They wrote games. Controlled hardware. Learned what made a computer tick. Connect a modem and talk to others. Sure, it was primitive, but at the time it felt as cutting-edge as space travel.

If I recall correctly, the Altair ran CP/M, and could run the early Zork infocom text adventure series.

All of my college peeps learned BASIC* while running the interpreter. We learned to fingerbone in the seq. to load from the tape, after the tape loaded I don't recall, but we then could get an OK prompt maybe from the BASIC interpreter. We used TeleType terminals w/paper rolls to print, with a tape reader. In parallel we learned Motorola MC6800 mach language on the new Heathkit trainers; our final task was to interface a speaker and play "Anchors Away" as my prof was an ex Navy instructor. *We learned BASIC, but by applying it to data and practical problems IIRC like physics of projectile motion, electrical like resistors, simple databases. Was a Pop Electronics reader from 1970 or so.