I feel the groove when I play bass. Even though I can't play the advanced stuff yet, I'm getting better at the basics and loving every minute of it.

> EDIT I should add Practicing bass has replaced my gaming 100%. I used to play games 1 - 2 hours every day. Now I practice. Timing is starting to click... now to maintain accuracy at high and low tempos...
The effect the bass in the music I love has always hit me as much as the lead / percussion - and now that I play the connection has grown. The more I play the better I 'get' music... not understanding it totally, but building a feel for structure, timing and sonic space. Super fun journey on the most badass of axes. When I pick up a 6 string 'tenor' guitar... it feels like a toy. (picked up an les paul (epi) that's supposedly heavy. It felt feather light (8lbs I'll guess) and tiny, with awkward tiny fret spacing due to the shorter scale)
Bass, when just below the painful or distorted thresholds*
sounds powerful and groovy - especially with percussion

Guitar and other instruments rarely sound as good to me, especially if they don't have the support of bass.
I look back and see many of my favourite groups from before I played/studied music - Led Zep, Rory Gallagher, Thin Lizzy, Tool, Queen, and most others had good grooves and tone in the bottom / mids. I'd say 60% of my enjoyment came from the drums & bass. Occasionally up to 100%.
SHORT ANSWER
I was asked to play to back up a drummer.... Best decision I've ever made, saying yes.
(*Don't worry, I wear ear protection when I'm up against drums)