Nintendo can't run their entire business based on your needs.
It's not your ass on the line when (like it does 50% of the time for Nintendo) the next platform transition back to 0 goes badly for Nintendo.
If I'm the Nintendo president I have to look out for my business first and foremost and I'm not taking that risk of a hard reset to 0. With only one hardware line (no GBA/DS/3DS to fall back on) and no other major divisions like Sony/MS have ... fuck no.
It's not like OG Switch gets 0 games and is rendered completely useless even if they do the 3-year cycle. Most/all Nintendo games can still run on it, and so could the same exact indie/third party games that were going to come would come anyway. That's likely still hundreds if not thousands more games coming to that model of Switch.
It would just likely mean initially there might be 5-15 third party titles a year that run on the "Pro" model that simply would not be possible on the regular Switch, and then by 2021/2022 you can have a more phased transition where maybe that increases to 20-25 games a year.
IMO that's fair all around.
You don't have to "reset to zero" with a new generation. Just maintain backwards compatibility and the whole OG Switch library carries over to the successor.