You can easily stay harmless and be in an anaconda, if you evade all the shooting.
As Schmu666 said: Credit do give me progression. I'm nowhere in need for Cr. But it's what I see as rewards. What's the point for me lugging bio waste or water, when I could be hauling Trit, making a decent coin in the process.
Just like in real life, you do in your time what gives you the most reward. Let's say for argument's sake, you are running your own business. You have an income of $100/h. The office needs cleaning every so often. You could do that during the day, or after hours spending your own time in there, or you could hire someone at $20/h and get that done for you. Because your time is worth more than the $20 you'd be paying someone to clean up. Doing it during the day is bad business, because instead of gaining $100 for the hour it takes you to clean, you are not making progress.
So you chose what is good business.
For the same reason we don't mine water. Not even for those lucrative 1500t mined water missions that pay you an eye watering 3m credits.
No, instead we mine 1500t of LTDs and make 2b credits in the process.
Same time, similar effort, better reward.