Testet is not full, there is space to join if you like. There are over 7.5K functioning nodes running the blockchain as we speak.
the Pi Network is like a digital nation, occasional celebrations and rituals are necessary too. Plus they are fun. For example, the (F)irst (F)riday of (F)ebruary each year is mod appreciation day, and March 14 (3/14) is Pi day. Having said this, rest assured that we are heavily focused in building all the necessary infrastructure for the Testnet and Mainnet.
When we get into mainnet people don’t have to use this app anymore as they can access the blockchain directly however they want. Of course this app will continue to exist and will offer a wallet and an entry point to pi utilities. But it will not be mandatory as they will be able to use other wallets too.