The most commonly known reason is security, and yes it can be considered very important if your garage or gate holds something valuable, when talking about security, we can take fixed code as an example, as you may already know, fixed code remote transmit exactly the same code every time button is pressed, which means if somebody is using a radio signal intercepter - which is like duplicating remote keyfob that works 100m or more - when you're pressing the button, he can record the signal and repeat when you're not around home, and open your garage or gate, so it would not be secure.
So rolling code here is come to rescue, since the rolling code part is encrypted and everytime the transmitted signal is not the same, so even if someone recorded one transmission, the receiver would discard the signal if the same code has been transmitted twice.
The other reason, however, is rolling code has some technical barrier, making manufacturing compatibles even more difficult for compatible remotes manufacturers, so original brand makers can keep much higher profit selling these original remotes, this is a obvious marketing advantage why more and more manufacturers are using rolling code remotes now.
Here we have studied the original remotes and provide compatible remotes that are just same as original, greatly lowered the remote's retail price while keeping exact the same security grade what original provides, there is no need to worry about security as it is just as secure as the much more expensive original remotes.
Nowadays among the major brand names, only Came Top432na still uses fixed code technology, while others such as BFT Mitto / ATA PTX-4 & PTX-5 have long transformed to use rolling code technology.
Of course there are many smaller brands made in China still uses fixed code technology by using PT2262 / PT2240 / eV1527 or chips like that, they work pretty well in most circumstances and are expected to continuing dominate the market for many years from now.