What is the origin of keyboards having very different feeling keys than pianos?
OK, let's go back to the late 1970s, when the electronic home organ reigned supreme, with worldwide yearly sales in the region of 250,000 units at the peak! Single manual electronic organs, with very basic 'arranger' like features, had been around for almost 10 years. (The Hammond 727 'Piper Autochord' was the very first in 1970). A few organ manufacturers, including Yamaha, were looking at making a truly portable instrument, with new technology that would allow battery operation as well as mains AC. Other non-music companies were also experimenting, Sony, Brother and Casio, for example.
The very first of these appeared on the market in 1980 - opinions vary as to whether Yamaha or Casio got there first. Yamaha simply used their usual organ type keys, and Casio did the same. Although there were a handful of electronic pianos using weighted keys, the bulk, weight and cost would have made such keys unworkable for a small, portable keyboard. And we should remember that the first Yamaha Portasounds were little more than toys with just a handful of styles and sounds. I don't think anyone at Yamaha foresaw how that market would take off - with its disastrous effect on the home organ business!
At first, most players were used to home organ type keys and the professionals wouldn't touch the instruments with a bargepole! So those keys were fine and indeed for most home players they are still fine, even though the instruments have developed beyond anything that the people working back in 1977/78/79 could have dreamt of. And there's a strong argument that says that it's more natural to play orchestral sounds on keyboards with organ/synth type keys.
As a personal note, I helped the team at Kawai come up with a single keyboard in 1979. It got to early prototype stage before the 'bosses' said "No-one will want to buy these things!"
Bad call, and it would be 7 years before Kawai released a keyboard.