If the intent were to protect the vaccinated, you would be correct, or nearly so. However, herd immunity protects those who can't get vaccinated, are especially vulnerable, or who fall through the cracks. We want to get so many people vaccinated that it will just become like measles, mumps, and polio. Something we used to worry about
https://scholar.google.com/scholar?hl=en&as_sdt=0%2C25&as_vis=1&q=vaccine+effectiveness+and+herd+immunity&btnG=#d=gs_qabs&u=%23p%3DbX3mNwSH5PMJ
The necessary herd immunity blocking the transmission of an infectious agent in the population is established when the prevalence of protected individuals is higher than a critical value, called the herd immunity threshold. The establishment of herd immunity in the population can be determined using the vaccination coverage and seroepidemiological surveys. The vaccination coverage associated with herd immunity (Vc) can be determined from the herd immunity threshold and vaccine effectiveness.