I went the other way, I’ve always had wifi only but for my new iPad Pro I got cellular. I wanted the option for later and for some travel we had planned, That was BC (Before Coronavirus) But I keep my devices a long time so I’ll still probably get to use the cellular option.
You can buy a cellular iPad and not put it on a data plan unless or until you need to. In the USA, I can add an iPad to my shared data plan for $10 per month before fees. So the data is “free” because it’s shared with the household phones, but you have to pay monthly to keep it connected to the plan.
Much depends on how you purchase the iPad. If you buy it from a carrier and you finance it with them instead of paying up front, you’ll have to buy monthly service for it.
If you pay up front or finance in some other way, that requirement goes away.
It seems that we don’t have a monopoly on terrible phone companies
That’s what I did, bought direct from Apple and didn’t activate it. The I got a Google Fi SIM card for it for data only. The plan was to use it when out and about, which obviously hasn’t happened but that’s ok.