Back on topic, I thought of an analogy for the simple groove vs "stretching out" issue.
Let's say you're an artist and craftsman who works in stone. Stone is your medium. You can carve beautiful statues, expressive works that demonstrate your artistic weight and vision in every facet and curve. As an artisan, you can also build walls and steps and foundations that are straight and solid and strong enough to last for generations - and beautiful in their own way, despite their simplicity.
So let's say I hire you to carve a statue of a loved one out of marble. I certainly wouldn't want it to look like the retaining wall beside my house. Similarly, if I hire you to build a stone foundation for a new house, I wouldn't want it to have the same kinds of expressive details as the statue you carved. I want a straight, level, solid foundation.
As musicians, we work all our lives to develop our ears, our chops, and our technical skills. Improvement and growth are usually achieved by continually reaching for that next bit of music that's difficult for us, working at it 'til it's well in hand, then moving on to the next bit. That progression almost always involves music that's more complicated and/or technically challenging. At a certain point, many musicians come to resent the fact that great numbers of listeners - "civilians" - don't see as much value in the complex and technically challenging things as we do. We love that music because we know what it takes to conceive and play it. But they don't look for the same thing when they listen. They want to be entertained, and far fewer listeners are entertained by hearing a musician challenge himself than are satisfied by something they can dance to, or relate to in other ways.
Somewhere along the line, each musician finds a place that satisfies him as an artist, or craftsman, or both. Maybe you play only jazz, or shreddy rock. And maybe you become an icon in your chosen style, or you spend your time happily playing to and for yourself. If you're happy, great! Maybe you don't dig the complicated stuff, and your big thrill is banging out endless streams of eighth-note low E's in a rock band. Good for you. Many or most find a balance of expressive artistic pursuits and craft-work playing - which can also be done at a very high level, but is not as individually expressive or, typically, as complex or technically demanding. This is especially true for bassists, due to the instrument's role in many styles. The only ones I feel sorry for are those who never grow past the idea that it's about impressing others with what you can do technically. They're missing out on a lot, IMHO.
Today I did a rehearsal for road shows with the latest iteration of the Burritos. I played a LOT of half notes, and not a single major 7th. (Well, actually, there are a couple lines in one of the minor tunes that contain major 7ths...) And I had a BALL. Great players. Tomorrow I'll start charting out some TOP horn parts (I'm a trumpet player too) for a thing next week. There will be a fair amount of soloing. I can't imagine plugging in parts from one of those gigs into the other. It wouldn't serve the style. I love that. I love the diversity, and I love the strengths of each of the styles. I like carving statues, and I like building nice, solid walls.