AdrianSz
Occasional Visitor
It is different because you keep on upgrading your system (laptop, mobile, tv) for years because you have either bugs or product lifecycle plan forces you to upgrade. That is normal update procedure.This is no different than having to reinstall your os (any os) on a computer when it begins to act insane. Same potential type of non-fixable bugs and glitches. Doesn't matter how many people are using their router (or computer) without ever having had a full reset/fresh install done, to troubleshoot in a logical manner requires that it be done.
When variables get changed, renamed, used differently, or with different switches, or different expected behaviors than how the firmware that was originally on the router used them, it is easy to see how things become buggy by not doing a complete reset to factory defaults and reconfiguring by not using a backup config file and also minimally and manually configuring the router so that it is secured and connected to the ISP.
When it comes to havoc(or insane behaviour), then yes disaster recovery procedure applies and you start over. But most of these procedures include often older backup as the starting point anyhow.
Evolving and correcting software include code refactoring, change of data structures, configuration files is normally done in controlled way so things does not brake for others and specifically for smaller deltas as monthly releases of the firmware.
But yes after long time, +3 years down the line change management becomes trickier. Software blocks, parameters gets obsolete making it hard to evolve and at the end are just missed and forgotten.
In this particular case, we are talking about stock firmware update that will happen every month until the desired quality is achieved. It should just work without the rather length procedure. Why? Because its pain in the butt reconfiguring everything, hardening the router, customizing it and potentially screwing up more things than what the new firmware is supposed to fix.