I think to achieve better yield, wider beds are needed. It also depends on what vegetable/plants people grow. If it is for crops, like corn, wheat, sunflower etc., the beds can be as wide as you can manage. There is no need to access the plants other than watering and final picking.

But for ready access, such as beans etc., a normal width is needed. Even in this situation, I'll still try to build beds as wide as I can manage. My tomato beds are about 6'-7' wide, to hold two rows of tomato cages. I can pick up tomatoes easily from both sides of the beds.

The less path, the more room to grow. Also, most of the plants do not like to receive the FULL sun from the ground to the top, but want the feet shaded. The tomato plants in the middle of my beds are doing the best, with the ones on the east side doing the worst.

Narrow beds and access path waste so much land/garden. About 1/2 of the garden space is used by the paths.

We run our own 'railroads' here and we are all different with different needs, desires, outlooks, and capabilities. For myself, I prefer few paths and then only about 16 inches...yes, I wheelbarrow down them easily.

I remember reading a garden book. The author did a comparison. Both himself and his wife keep different beds. His wife is light (~100 lbs.?) and walks on the garden bed. The author does not.

By the end of season, the author claims, his beds (no walking) yields about 13% higher than his wife's garden beds (casual walked). I do not know how scientific his study is. But I highly doubt it. There are so many factors other than walking the the beds a few times by a light person.