Additionally, as much people like to harp about "telcos focusing on connection-oriented protocols while we ran loops around them with packets", the reality is that NCP and later TCP pretty much focused on emulating serial lines around, and one of the earliest ways to access ARPAnet outside of machines directly on it was through calling into a TIP which set up bidirectional stream from your modem to a port on some host.
The idea with packets is that you don't need to reserve N bit/s of each link along the route to whatever system you're talking to; instead you just repeatedly say "here's a chunk of data, send it to X". It's not really relevant that the typical thing to do with these packets is to build a reliable stream on top of them, what matters is that everything except the endpoints can be a lot dumber.
This still requires you to set up a connection beforehand, but doesn't require you to reserve resources you might not be using.
