I suppose what it boils down to is that the place was code heavy - even today, it remains the most heavily coded and randomized MU I can think of - but the code, by and large, set up rp rather than served as a substitute for it.
Singers cut crystal. If all went well, they would need to go see a Sorter and get their crystal Sorted. The Sorter had a bit of leeway as to how much they could mark the sale for - so keeping on said Sorters good side was definitely advisable. Also, they would acquire resonance in the ranges - so that needed to be dealt with by not being in the ranges; thereby meaning that you couldn't always be hunting by yourself.
Your gear needed maintenance, so that meant interacting with Sled and Cuttertechs too. Plus, Sled and Cuttertechs provided the most viable outlet to spend all that money you made by kissing up to your Sorter: new cutter parts, enhancements on your Sled - all of which had in-game effects of helping you fly or search, influencing the quality of your cuts, etc.
And that's if everything went well. If something screwed up, you could crash, damage your sled, break your cutter, or what have you - which would require additional rp since no one classification could do everything - Singers sang, Sled Techs worked on Sleds, Cutter Techs worked on Cutters, Medics worked on Singers. If you got coded damage to your gear, or to yourself, you couldn't do anything until one of the support staff cleared it for you.