I don't get it

Desingers, no matter how talented, can be of a certain mindset and nothing will sway their beliefs. Like Milpai said, try a nice sized section of tile or wood to rest the speaker when upon the carpet. It could very well be that the designer tried all manner of footings and found the best solution (doing all the homework for you).

By the way, unless you have the proper depth and know what you're doing, I wouldn't drill into the bottom of any speaker.

All the best,
Nonoise

Bander if you want user experience please tell us the speaker brand and model. Then with some input from others on YOUR speakers you might as your op states 'get it'.

I've seen this happen reasonably often in audio for speakers, preamps & power amps. A certain speaker manuf was wary of users trying anything other than the hard rubber (or was it plastic?) & very sturdy feet that were factory-fitted. The whole speaker system was designed as 1 holistic component which included the feet.
I also got a very similar response from a preamp manuf - he told me that his factory-fitted feet were the best & that he had taken care of vibration control in the chassis & overall product & that adding fancy-shmancy feet would do nothing to improve the sonics.
Same deal with an amp manuf who said that using metal feet would make the sound of his amps bright & that his factory-fitted feet (very sturdy) are the best.
Quite common for the manuf to say this but as I found out, they are not always right! Experiment & listen & you might find a better feet solution for your application.

You might try what I did in my last home. Check what is under your carpet. Is it cement, plywood, linoleum? I had old hard linoleum under my carpet. I have a tall set of Dunlavy SC3's. I went and bought 6 metal cones, three per speaker. I had 2 cones on each left and right rear corner, and one cone in the middle in the front edge. The sharp point of the cone penetrated the rug and coupled directly over the hard linoleum. One last thing; you will notice that with only one cone in front, that the speaker has wobble room because there is nothing supporting the front left and right portion of the speaker base. I ended up getting small pieces of cork, about 3 inches in diameter, and gently snuggled it in each front left and right corner. That made the speaker more stable. I think that you'll find the direct coupling of the speaker/cone tip/floor a good solution. It was for me. Good luck.

Thanks for the input and comments. The carpet is on an oak floor.I've decided to place 1 inch thick non resonant stone tile (perhaps granite) under the speakers and raise the speakers at all 4 corners with cones of some sort.