Shops come and go. MSC's have deadlines with clients at the end of each month, quarter and year. We are generally not privy to the details. However, most shops are posted well before their deadlines and the next round not posted until the previous deadlines have passed. The end of a quarter is about three weeks away, so we should b seeing fewer shops available from now until the end of March. More will be posted for April.
If you really want to keep yourself busy shopping, you will want to expand well beyond the iSS platform. What is posted on this site is only a small fraction of what's really out there. For instance, I've done nearly 80 shops so far in 2018 and only about 10 have been through iSS.