No, it ain't the cheapest keybed they make

...and, as I said earlier, key feel will always be a
personal choice.
If I wanted semi-weighted I'd get a Tyros, which has the best action by far of any arranger (IMO), but I like the fast and even touch of the PSR.
And besides...all light actions feel even lighter to those used to semi-weighted keybeds...you adjust after a bit...just like going from non-power steering, to powered.
Pros have no problem adjusting to different actions...guitar players do it all the time...some like the strings laying on the frets...some like them so high you could limbo under them.

You can't equate light with cheap or flimsy; not in this day and age...my PSR's have stood up to a lot of playing, far more that the usual home user, and maybe even more than most pros...and I'm, a piano player, so I'm not real gentle.
Some people, in duos, for instance, are lucky to have someone help them with their overweight arrangers...those who perform solo, don't have that luxury, so weight will be an important consideration....hence the popularity of the PSR line for pros.