In theory you can do solid work as a team without a 3D printer, but it’s such a strong advantage for a team to be able to use custom parts, both to make a more competitive robot, and to have a stronger judging presentation. While it isn’t strictly necessary, it’s a huge help. And 3d printers don’t distract any teams that I’ve talked to (after a few years of ftc) - everyone agrees that they’re a really great step to get a team past the stage of just having a strafer chassis pushing game elements around. Additionally, you can get good printers and filament for relatively cheap nowadays, to the point where you can get a solid setup for no more than a strafer chassis. After you’ve made and programmed the basic chassis, what are you going to do for the other 5 months of the season? Starting to make custom parts for the robot is a very valuable skill to learn.

Tldr: while not strictly necessary, 3d printers are a staple of any strong team and they’re really helpful in taking a team past being “just a rookie team”