I often get the impression that Nintendo is afraid of their own past. When there are a lot of (cheap) re-releases available it could potentially hurt sales for current full-price titles if players are busy with classics.
Other than that I never found a reason for not making all old (first-party) games available for download in one shot. Costs (opposed to past cartridge releases): $0 …and potentially a lot of sold licenses. Zero risk. For third-party titles it's more complicated with a lot of different rights holders – but even that could be managed.
The Virtual Console releases on Wii(U) and 3DS are so incomplete (for example not a single official GBA title on 3DS besides the 10 ambassador exclusives). So much wasted potential.
If they do not want to publish a GC/Wii emulator or GC/Wii ports on the Switch, it seems they do not want to earn money this way. Wii consoles are cheap. Most used games are cheap… so what? Play them on Wii and Nintendo doesn't get a penny. Their problem.