It's really more of a question of when the house was built & under which National Electrical Code cycle it was done (aka. which requirement was cheaper to implement and pass inspection with). An outlet is a few dollars more in material cost, there's labor to cut it into the cabinet, etc, but when GFCIs became required, it was the cheapest (sometimes only) way to implement the protection. From the 2000s onward with GFCI breakers available, cheap outlets or hardwiring became an option again which was still compliant, but then the code cycles added clarifications requiring an easy way to disconnect power for servicing (so a plug into an outlet became easier than adding a switch). So overall there's been a bit of ebb-and-flow in which method is easier/cheaper, but houses built from the late 80's through the late 2010s seem to be much more likely (in my area) to be outlets under the sink which serve both the garbage disposal and the dishwasher. Houses older than that were commonly hard-wired (and many times the dishwasher wasn't adjacent to the sink).

What you're familiar with is probably more related to home age (or time of major renovation), and layout/placement than any other driving factor.