Really? There are an awful lot of people out there who do just that... ie. plug in something that uses USB1/2/3 into a USB-C Mac. I bought a load of USB-3 to USB-C dongles for less than $5 each.Most people buying a MacBook Air likely aren’t plugging in anything that needs a dongle.
MacBook Pro on the other hand would be a better target for lack of ports, although Apple is going to improve that soon.
Let me give you two examples.
1) How do I get the updated maps for my car onto a 64Gb USB-3 stick?
2) How do I get a route onto the microSD card for my TomTom Sat Nav (for my Motorcycle)
Ok, so my use case is different from yours but there is no reason to state that 'Most people buying a Macbook Air...' I know two colleagues who have new M1 MBA's who use dongles all the time. I'll be upgrading my 16in MBP to an M1(or M2 or whatever CPU it uses) when it is released. If I need to use a dongle or two then fine.
At least it is a lot better than the bad old days of SCSI. Now which terminator do I need today?