While a license like MIT gives you the most possible freedoms, it also gives the freedom to derivative works to remove all those freedoms. A copyleft license doesn't grant those kind of freedoms so it can try and protect and keep the four essential freedoms[0] in derivatives. I do agree that it is more difficult to commercialize copyleft software. In an ideal world, we would be paying for copyleft software, not giving it away for free.

[0]: https://www.gnu.org/philosophy/free-sw.html