Most of the other responses are missing the point of your question. You really asking why central banks don't engage in targeting the price level, rather than price changes (=inflation). In price level targeting, they'd aim for higher (lower) inflation next year if they under-(over-)shot their target this year.

Academics and have studies the pros and cons. I don't have time to post summaries, but maybe someone else can step in:

https://www.stlouisfed.org/-/media/project/frbstl/stlouisfed...

https://www.ijcb.org/journal/ijcb2002_3.pdf