Vampyr, on 2018-March-13, 09:06, said:
Unless they are playing a system where 1 level opening is unlimited, pd is limited.
He is limited with 17-22. Therefore you can pass if you believe even a 22 count would not make a good play in game.(in practice almost everyone opens 2♣ with 22)
You may ask "then why respond at the first place?" Answer is easy - You may hold a hand that would improve a lot had you found a fit, and for the rest you were willing to bail out once you believe you improved the contract.
An example:
JTxxx
xxxx
xxxx
Void
1♣--1♠
2 red--pass