I see this a lot but wonder what specifically it is that makes these 3rd party firmware that takes a percentage of your mining A LOT better?
Using custom firmware my miners run cooler at the same hashrate and consume less power, the auto-tuning per chip allows such a thing to happen, while on stock firmware the best you can do is find some stock version that might allow you to change the voltage and/or frequency of each board alone which doesn't bring the miner efficiency nearly as close, just a random example would be S9s running at anywhere between 70-75w per TH which you can't possibly achieve without tuning every chip differently.
You can even have two different profiles to switch between automatically during day/night, this is very helpful for people who pay different power rates at different times of the day, or for fall/spring seasons when it's warm around noon only, on S9 I can set 14TH mode from 6PM to 12PM and 12TH for 12PM to 6PM , both modes will be more efficient than the stock.
The auto-tuning and profile switching is something I personally use which is why I talked about them in detail, the rest of the features such as immersion cooling, overclocking, full SSH access, and whatnot can be found on that custom firmware webpage.
I also can't tell why other people use custom firmware, but I'd assume most of them do it for the same reason, I'd imagine that by now most people who still run S9 or any of the 17 series probably run it on custom firmware since the stock settings are not profitable for most power rates out there.
With stock firmware, if you leave one dead hash board on the miner it will cause issues such as rebooting, taking forever to boot as it has to test to the dead board a dozen times, it's even worse on Whatsminer as you can't just unplug a power cable and you are forced to take the bad hash board out of the miner which messes with the airflow, some custom firmware have the option to programmatically disable the bad hash board so the miner will treat it as "unplugged", I had a long conversion with Whatsminer's support admin regarding this, and despite the fact, that people report this issue to them all the time, they still did not solve it yet!.
The lack of features isn't just Bitmain's issue, even Whatsminer's firmware is pretty basic, it's somehow better than Bitmain, but you can only run the miner on 3 modes, high, normal, and low, the low is just TOO low, so for M20s you go from 68th to 40 something TH, and for the high, you go from 68th to probably 80 something, so you have a total of 3 profiles to choose from, which is why I decide to let my Whatsminers run a bit hot during the summer because I can't afford to lose nearly 40% of the hashrate, I could really use a profile that sets the miner at 10% less hashrate, anywhere around 55th for M20s or 45th for M21s would really do me good in the summer and around noon for except for winter season.
But well!, they don't want to bother with that, so when and if someone makes custom firmware for Whatsminer, I would certainly want to use it.
Stock firmware doesn't even allow you to change the fan settings, let alone do something else with your miner.
Personally, I use AwesomeMiner distribution of Vnish, I can either pay 1.8% and still have to buy AwesomeMiner license or pay 2.8% and get AwesomeMiner for free, I have already bought a license for 200 miners, which I can run at 1.8% and the rest I pay 2.8% fees including license, if the stock firmware allowed me to do the things I can do with this custom firmware, I would most certainly want to keep the fees, but until that happens, I'll continue to use custom firmware.