Removing springs can of course make it easier for using the Trem and its NOT unusual to use 3 springs at all. It makes sense for PRS (and others) to put 4 in at the factory so you get 4. Its easier to take 1 out than to try and find one to put in if you prefer 4 springs. I guess PRS (and others) could supply the extra spring in with the case (or Gig bag) candy.
Finding the balance between having a 'stiff' bridge and 'ease' for using the Trem arm isn't necessarily that simple. If you take too many springs out for example, if you try bending the strings, the tension of the strings will pull on the bridge which will cause it to lift up - meaning you have to bend further to counter the movement in the bridge - the strength of the springs isn't enough to stop the bridge moving. Having more springs will mean that the bridge stays level when you bend - the tension in the string isn't enough to move the 4 springs when you bend.
It really depends on the player, their style and preference. 3 springs can be enough for someone as they rarely do full or more tone bends and get used to bending that little bit more to compensate but they do use the tremolo a lot more so prefer not to fight against the 4 springs trying to pull the bridge back. Compared to another person who rarely uses the tremolo and want to keep the bridge from moving when they do big bends or hit the strings hard and when they do use the Trem, its more of a little wobble than big dive bombs.
Point is, just because a guitar comes with 4 springs, doesn't mean you have to stick with all 4 springs. It really depends on user preference and how much of an impact dropping out a Spring makes for that user. As long as you set it up right - may need to adjust the claw to pull the bridge level again - intonation should still be great and, if it suits your style better, playability and ease of use should be improved. String tension has an easier job of pulling the bridge up with only 3 springs so tightening the claw is needed to compensate and to bring the bridge back down level - full bends though may need a to be bent up a bit more to reach the right note. If you find it easier to use the Trem, then string tension from bending will find it easier to move the bridge too.
It comes down to your preference. These guitars can be set up with 3 springs if you prefer and you should find it easier to use the tremolo as you are only pulling on 3 springs and not 4. You may have to adjust your string bends too, bend a bit more to reach the right pitch because there is one less spring pulling on the bridge to keep it from moving, keeping it 'stiff'. Finding the right balance for you is important and if 3 springs is better for you, then that is what you should do. You don't have to stick with 4 springs just because the guitar came with 4 springs. If you do drop a spring out, just stick the 4th spring in with the case candy to stop it getting lost and easy to find if you need it or if you do decide to sell/trade in the future.