I think some of them have. I’m pretty sure I remember having some like that. My not-very-educated guess, is that they tend not to lately because they’d complicate the range’s design and take space from it, and the plugs would end up either being custom replacement parts, or maybe be hard not to clash with the range’s own aesthetic. Also part of my guess is that the designers assume the kitchen itself will tend to be well-equipped with power outlets and that that’s the appropriate place for them.