The answer is entirely on your use-case and your intended infrastructure.
If you intend to use multiple different assistant environments like Google Home, Apple Home, Alexa etc. Then Matter theoretically makes it easier to share devices and have these environments play nicely with each other.
If you're sticking a single environment then it doesn't really add much over things like Zigbee or Tasmota or ESPhome, which already have the benefits of fully local control. If you ever decide to transition to another environment it should make it easy to migrate though.
If you're using something like Home Assistant which can use any of these devices and export them out to google, Alexa, apple etc. then the multi-environment argument doesn't really matter.
The other argument is future proofing. Theoretically everything will eventually move to matter, until a new standard arrives to challenge the status quo again. So being matter-ready at least makes you future proof in that sense.
Another consideration is price. I haven't looked in to it myself but wifi stuff is cheaaaap. And if you have a handle on flashing Tasmota then adding a lot of smart devices can be done on the cheap. I presume matter stuff for now might have a premium on top being new, but that's just my guess. I know Zigbee and zwave are generally a little pricier than wifi devices.
Matter is also pretty new, so it may have some teething problems which may introduce stress and annoyance, but that will iron out soon enough I would think.
My personal opinion is go for local control where you can and if it works for you then no need to make any changes if you're only doing those changes to follow the crowd.
In regards to returning stuff with provisioning info stored in it, these devices should all come with a method to wipe the data. Usually for bulbs it's something like turning it on and off 6 times really fast or something like that. If you flash devices and don't want them any more then I reckon the warranty would be void. Sure the shop you got them from likely won't check and will happily take it back but morally it's a bit questionable. I'm sure you'd be able to flog them on Facebook marketplace or whatever your local equivalent is. Enthusiasts love preflashed devices.
Disclaimer: I have no first hand experience with matter so happy to be corrected if I've been mislead.
I use this approach myself but am starting to reconsider.
I have an Asus PN51 (NUC-like) minipc as my server / brains, hosting all my dockers etc. All docker containers and their volumes are locally sorted on the device. I have a networked QNAP NAS for storage for things like Plex / jellyfin.
It's mostly ok but the NAS is noticeably slower to start up than the NUC, which has caused issues after power loss where Plex thinks all the movies are gone so it empties out the library, then when the NAS comes back up it reindexes and throws off all the dates for everything. It also empties out tags (collections) and things like radarr and sonarr will start fetching things it thinks don't exist anymore. I've stopped those problematic services from starting on boot to hopefully fix those issues. I've also added a UPS to avoid minor power outs.
