There are good reasons for both ways.....
As a standard Van's Aircraft practice, all company demonstrators are always parked with the flaps down.
I have seen comments along the lines of "If it is someone I trust getting in my airplane, I trust them to not step on my flap" (or something similar).
That trust works........ until it doesn't.
At Van's, we have the experience of many thousands of people climbing in and out of our demonstrators each year. At events like OSH, we can top that in a week.
On a regular basis, after just having had a persons full attention and explaining to them where they can and can't step or grab, there are a certain percentage of people that 5 seconds later will step or grab exactly where you just told them not to.
So for us, double the wear and tear on a flap motor is a small price to pay compared to the effort involved in repairing and painting a damaged flap (best case.... worse case being an unairworthy airplane far from home).
It is why we affectionately refer to our aircraft as "Adult playground equipment", and it is also the reason that after a few years they tend to show signs of the use and abuse they get.
This is not a complaint, it is just part of the business. Often times when people are encountering our airplanes (maybe an RV for the very first time) they can be a bit excited, which could be another factor.