The IDE has a setting to always turn it on for new projects. That was a setting I always enabled on new installs. Along with a switch to use SDI instead of MDI.
In my first job, I was given a VB6 project to maintain which had a mixture of "Option Base 1" and "Option Base 0" (or unspecified, this being the default), with occasional "On Error Resume Next". This specifies the index value for the first item in an array, i.e. you could choose the default European building floors (ground floor is 0) or American floors (ground floor is 1) -- per module!
I had to convert everything to "Option Base 0" before I could start fixing the reported bugs, it was far too confusing following the arrays passed between modules being indexed starting at 0, then 1, then 0 etc.
The existing code was written with 0 or 1 as required (except where there were bugs), and frankly I think it's was better anyway to use 0 everywhere rather than LBound(x).
Do notice Option Explicit. That is like disabling 90% of the magic that causes unmaintainable code.