There are very valid reasons no not upgrade Chrome...
If you are running flash, especially in full screen kiosk mode, it is not feasible to upgrade Chrome.
Because Google took out a user's ability to always allow flash from specific sites using the chrome://flags/#enable-ephemeral-flash-permission flag in v. 69, anyone using flash in an unattended kiosk needs to use an earlier version. (Never mind that Google doesn't even have an ftp site for old versions, you need to get them from who.knows.what.malware.lies.here.com.)
See https://productforums.google.com/forum/#!msg/chrome/7y0gbgs06L8/3ehByJReGQAJ or many other posts from aggravated users.
So much for doing no evil. I wish I could take back the many thousands of $ I gave Google, buying many Nexus'es, Pixels, storage, Fi subscriptions, etc...