Obviously, Wii and Wii U games will be available as digital downloads (just like they were on the Wii U), but many of us own Wii and Wii U games already in disc form.
How do you figure that it's "obvious" that Switch will get WiiU games through the Virtual Console?
PS4 doesn't have PS3 games on PSN. (There are PS3 games that have been HD ported to PS4, but that's something different.)
Xbox One does have 360 games, (and even lets you play them for free if you have the disc) but that's only because they figured out how to do it, and Spencer said he didn't think it was possible.
Switch has different architecture from WiiU. So they'd have to use some form of emulation. And emulation requires more powerful hardware than you'd normally need.
And keep in mind that WiiU games are Generation 8 games. Generally should be more difficult to emulate than PS3/360 games. Plus Nintendo have been porting WiiU games to Switch left and right.
In conclusion: No way is Switch getting WiiU games on the virtual console. Only if they've been ported to Switch.
That means no disc drive either.