Satellites are complex machines and there's a lot of engineering work that goes into figuring out exactly what to build. The goals for a mission are usually set by a client/end user: e.g., I want images of San Francisco at a resolution of 5m/pixel or less.
Engineering work goes towards simulation and analysis to figure out what the size of the solar panels are that you need to generate enough power on-board to power the camera, what the size of the battery needs to be to make sure that the satellite keeps functioning during eclipse, what the size of the thruster is that you need to keep the camera pointing at the right spot, etc.
Once you've figured out what you need, the job of finding a vendor that has your part involves wading through their websites to find data sheets, calling them, emailing them etc. It's a really time-consuming process and all you want to know is if there's a part that matches what you need, within your budget, that has heritage in space, etc.
The engineering work is iterative because the subsystems within the satellite all depend on each other. Hence, you're doing this search over and over again. Usually, you just end up making sub-optimal choices.
We've tried to explain the search problem in the following video: https://www.youtube.com/watch?v=FlHEoq7utW4. The low-hanging fruit comes from the fact that a lot of data is already available online, just completely unstructured.
The idea of tying this in with simulation tools is that it allows you to do things like programmatically figure out what happens to your design if the vendor you've picked for e.g., your battery fails to deliver. This kind of sensitivity and robustness analysis is very important during the design process, because it allows you to reduce uncertainty and figure out the main risk items that you need to devote engineering time to.
Bit a long explanation, but hopefully that gives you a better sense of the immediate problem we're trying to tackle for engineers.
For vendors, the pain simply comes from not knowing where their users are, i.e., teams that need the parts that they are selling.
Does this help explain the pain better?