• There is a minor safety issue, as portable units are - by definition - easily movable and can be jostled, tipped, etc. A range isn’t going anywhere.
• On a range you will typically have four burners, two front and two rear, with controls for all four on a common panel which is easily accessible at the edge of the counter. Each portable induction plate will have its own control.
• As others have pointed out, a combined cooktop (in the US) will generally have a dedicated 30-50A / 240V circuit supplying power to the group of heating elements. Unless you have asked for multiple circuits when you built your house, there will often be a single 15A/120v (or, in the last 20 years 20A/120V) circuit supplying all of the receptacles in your kitchen. If your house is older than ~1975 or 1980, the refrigerator may be on the same breaker as the receptacles. Even with a 20A/240, it means you’d be sharing the circuit with a countertop microwave oven, stand mixer, toaster, coffee machine, sous vide, etc, and possibly even the overhead lights and lights/receptacles in adjacent rooms.

I made the note about special circuits because when I had the kitchen in my 1960s house redone, I had 4 separate 20A circuits run, plus the fridge, plus the lighting circuit both separate. Two pairs of the outlets are actually on adjacent breakers so that, if I were crazy enough to do it, I could get a 240V/20A service with a custom (and definitely not UL rated) dual plug. I’ve never done that and, though it would be possible, it’s a terrible idea because it’s not a common breaker but two individuals and they should really be able to trip with a single breaker if used that way.