because majority of wallets have not yet implemented SegWit. i am not a core user (so correct me if i am wrong) but even in bitcoin core there is no "easy" way for regular users to create a SegWit address. in other words it is not as user friendly.
other major wallets like Coinbase, blobkchain.info and lots of desktop wallets have not yet released new versions to enable SegWit.

some of them that did release it like Electrum, it takes time for people to upgrade to those new versions.

and finally when you have funds in a regular (legacy?) address and you want to move to SegWit you need to transfer your funds, and that requires paying a huge fee based on the current mempool status.

One plan was already deployed, that was the segwit activation, but wallets and exchanges are still taking to long to adopt it. I mean do you have a segwit enabled wallet right now? If you had, and other users had it to, and exchanges, etc, the fees would be a little lower, just because of that.
The other plan, is of course the development of the Lightning Network, and that one should solve the problems once and for all. The problem is, that no one knows when this will happen, and people are not very patient normally. Bitcoin exploded to soon, and most people are just searching for fast profits, and don't understand that they need to wait for the technology to mature.

top secret shit there

https://en.wikipedia.org/wiki/SegWit

how to

https://bitcoin.stackexchange.com/questions/57832/how-to-generate-segwit-address

then again, first learn about what is an address

https://en.bitcoin.it/wiki/Address

...

In general its best to print everything at bitcoin.it, and keep it near the toilet, so you have something to read, while waiting, ...