It depends on the field, but in several fields (eg life sciences) if you do not keep output up, you will be unable to attract grant funding or industry funding.

It depends on the field, but in several fields (eg life sciences) if you do not keep output up, you will be unable to attract grant funding or industry funding. Without funding, you cannot really do any work. Additionally, without funding or papers, you will not be able to recruit students because students want to get their name on papers and want to work for prestigious groups or labs. Without students, you will be doing all the grunt work on every project you take on yourself which will eat up all your time. You will also have newfound responsibilities such as teaching classes, and the university will expect you to teach more classes if you are not bringing in grant funding or doing prestigious research. It is not a free ride, and universities will take space from you and give it to people who can produce if you can't as space is scarce.