That they don’t charge a fee on swap volume, doesn’t mean that they’re not important to Jupiter. Swap volume is the main function of Jupiter, and nearly 95% of users only use the swap function.
From a business strategy standpoint onboarding regular trading / swapping users is of vital importance to Jupiter.
It has been the strategy of tech companies for over 20 years to onboard as many users as possible without having them pay, often even paying to onboard them. They know having millions of users will make their company valuable and they can also monetise the platform later on.
For example Twitter didn’t have Ads on their platform the first 4 years, until only later when they were already big. Jupiter could theoretically add a 0.1% fee at some point in the future and make $340 Million in swap revenue from $340 Billion of volume.