I'm sure you remember the foot is constructed of arches (from the toes to the heel is the longitudinal arch and from the big toe to the little toe is the transverse arch). Your weight depresses these arches slightly with every step, just like pressing down on the toilet plunger compresses and deforms the suction cup end.
Instead of sticking you to the floor, however, like this guy...
this spreading or widening of your foot is an energy absorber. (But wouldn't it be cool to go up the sides of buildings like SpiderMan or a tree frog with your sticky suction-cup feet?)
When you land a jump, your feet spread out for a couple of very sensible reasons: to distribute your weight over a wider area, to stabilize your landing, to maximally disseminate the landing force. Don't believe me? Then try jumping in stilettos. Have you ever tried on new shoes that felt great as long as you were sitting, but absolutely killed when you stood up? That's your transverse arch spreading out like a suction cup.
It would seem therefore, that pointe shoes do not make any sense.
Take them out of the box and they are very rigid. They are made of cardboard and glue and covered in satin; some have a carbon-fiber shank in the sole to provide support and longevity to the shoe. When they are new they are very supportive to the foot, but most uncomfortable. Each dancer has her own personalized method for softening up her pointe shoes: hammering, scraping, closing in a door, warming and reshaping, etc.
When pointe shoes are new and stiff it is very difficult for the transverse arch to widen and flatten out and you feel it as compression. Pointe shoes are at their peak in mid-life (just like people). This is when they have softened enough to allow the toe box to widen a bit for the natural rhythms of the foot and yet not so soft that they can't provide the necessary support for dancing on the tips of your toes.
You know all this already, though, from your own experience. Your gut tells you that these Jimmy Choos
will probably be more uncomfortable than these Keens
and now you know the biomechanical reason why.