Well I agree that what you say is factually correct that study permit isn't a direct route to PR.
But,
students have been coming to Canada (and thereby bringing in lots of dollars) with the dream of becoming PR some day by getting PGWP and then qualifying through CEC. in fact Canadian schools and their agents have been using the "PR path" to get students to Canada. I have witnessed this first hand. In comparison with US, the best thing Canada has to offer is PR (with its colder climates, lower wages etc. etc.) Give me a good reason why would any student in future want to spend dollars in Canada if they see getting PR isn't an option anymore. Why would they not got to US or any other country if they ultimately have to return home. I agree there might be students who just want to come, study, work for a bit and go home, but definitely a lot more who want to stay here permanently hence the discussion.
Before 2015, there was no discussion on this topic - study permit does not lead to PR. Why? Because it actually lead to one. it lead to 3 yr work permit, was easier to get 1 yr Canadian experience in 3yrs and get PR with nothing to worry about scores or ECA.
The govt. will definitely see this as a problem. I believe if there is a fall in international students there may be some changes even if its scoring a bit more with Canadian education or work experience.
I agree factually Canada does not owe Citizenship or PR to any international student, but same way Canada does not need to bring in refugees. But everything is not fact, sometimes there is more to it.