Do I understand correctly that on the candidate side the person can go through a sequence of interviews without the possibility of actually meeting a hiring company? Also that you only work with students?
The people using Interviewing.io are typically using it as a means of practicing interviews in a low-pressure setting. Their goal isn't to get offers from companies, but if it leads to that, I'm sure they don't mind.
Also, they don't just work with students. I've used them, and I've worked professionally for several years.
We have 2 pools: a practice pool and then a pool where you get guaranteed interviews with employers. If you do well in practice, you can book real interviews with any number of top companies who've come to trust in the quality of our users.
This goes for both senior engineers, and more recently, students.
Do you have stats on how many of your customers are in their 30's and 40's? I would think that demographic would find practicing very useful since they have been out of touch with algorithms for a while.
Also, they don't just work with students. I've used them, and I've worked professionally for several years.