Because that initial "DO IT NOW" respec screen is broken, and has been since they did the skill redo on Tribble.
You'll have to do another respec, and the other 50 points of cap space will magically reappear and let you spend it.
The problem really seems to be that we got refunded all our skill points, but there are still 50 skill points we have to earn before we can really "finalize" the spec.
Not sure if you can get the Quantum Slipstream with only 72,500 if you spend all those points immediately after they were refunded, but the moment you actually respec, you may have 50 points that you previously simply didn't use, and now have to work into your build. That's very messy and it will cause a problem for many players.
Well, 72750 - 72700 = 50. So there are 50 points you still have to spend on something? So you have to re-respec to a combination of skills that let's you use the final 50 points as well?
Thats not working.
When you look at the skilltree there the the columns of the tiers and on the top you have the max ammount of skillpoints that can be used for a tier. And in the T5 column i still have 72700 points although I can use 72750.
When I spent all my points it says I spent 72750/72700 points.
If you're flying a Vesta with enough Vesta consoles, the slipstream is replaced with "Chroniton-integrated quantum slipstream", and re-sorted alphabetically. That one caught me by surprise when I moved to it.