Change wheel or tyre?

Please excuse the complete newbie question, but I read on here about folk changing to thicker tyres for the winter, or temporarily for gravel rides etc. Is it normal to just change the tyre, or do you swap the whole wheel out (which seems like it would be much quicker to do?).
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a new bike
a new wheelset...complete with sprocketts/discs/qr's etc
changeover tyres...keeping a large supply of spare inner tubes and not buying hard to change tyres
And the first two options have the added benefit of deliberating/agonising over what to buy for hours/days/weeks/months.
I've also got new wheels for it fully fitted out for on road tyres as my daily spare bike..
Bike 1 (Broken) - Bike 2(Borked) - Bike 3(broken spokes) - Bike 4( Needs Work) - Bike 5 (in bits) - Bike 6* ...