Because the people you'll be matching with deserve to see real, settled accounts, not someone who signed up an hour ago to test the waters.
Social networks have the same problem: someone creates an account, fires off twenty connection requests in the first hour, then never opens the app again. That noise hurts the people who are actually here. So broader network recommendations wait until 14 calendar days have passed since signup.
During those 14 days you can still do almost everything: view your chart, accept incoming connection requests (sometimes existing users find you through other paths), use Ask with Sparks or Premium, and explore.
During the waiting period, you do not appear in broader network recommendations. Free members cannot initiate a connection request yet; Premium members can send one under the current Premium permission rules, but the account still does not enter broader recommendations until every gate is complete.
It's a small friction that makes the whole network feel calmer and more deliberate.