What's wrong with this idea?

After reading the “Do you always file IFR?” thread, I
began thinking about some of the benefits of IFR flight that some
mentioned. The two biggest being that you can cruise at altitudes that
decrease your chances of colliding with a VFR aircraft and
you’re guaranteed flight following. If those two benefits
outweigh the downside of flying IFR (in your opinion), wouldn’t
it make sense to always file and fly IFR, even if not legal to do so?
Specifically, I’m thinking that if you follow these 2 rules:

1. Fly under VMC conditions only (i.e., treat it just like a VFR
flight for visibility and cloud clearance).
2. If given a clearance you are unable to follow, inform ATC
“Unable” and get another clearance, or, as a last resort,
cancel IFR.

then it would be safer to fly IFR than VFR, even in an aircraft that
is not IFR certified. Taking it a step further, it would also be safer
to fly IFR than VFR, even if you aren’t IFR current.

Besides just being illegal, is there anything else wrong with this
idea?