Sophia
Definitely agree that beginners can use a low-end keyboard. I use a portable keyboard at home. I also have access to Yamaha Clavinova DPs, upright & grand pianos at the place where my lessons are held which is a fair compromise.
Suzuki Associations around the world had decided that an acoustic piano produces a natural sound which would help students develop musicality & expression. Today the default piano sound coming out of a digital instrument is very close to that of an acoustic piano. The touch of the weighted keys on a DP is very close to a piano.
Whether somebody would continue piano after 1 year is hard to answer. I know people who had a teacher for a while and quit (never touch an instrument again). After a while they find that the music lessons get monotonous. The pieces they play along with scales & other exercises boring. The son of a family friend who was in Suzuki years ago is still play which is surprising.
I play music mainly for stress relief. I'm not limited to playing the teacher's assigned pieces. Finding pieces at your level is not a problem. People share sheet music on social media sites including Facebook & piano forums like this one. Once you learned to read at a basic level, you can find all sorts of interesting pieces online.
The place where I grew up people have a lot of respect for teachers. Practically everybody who can play an instrument to a certain level learned from a teacher. By default people would learn Classical pieces before anything else. They'd get advice from a teacher when choosing pieces. I download some pieces and learn on my own.