Forgive me if you already have heavy aeroplane time, but I have assumed not.
Not every helicopter has wheel brakes, so perhaps you might not be aware that it is common for larger aircraft with wheels to release brakes for improved cooling after the chocks have been installed. You might even have noticed some light aircraft with a padlock that prevents easy chock removal.
I have heard of other cases where untrained or careless people have removed chocks for other uses and placed the aircraft at great risk. In particular, I am aware of a RAAF C130A at Kainantu, PNG where chocks were temporarily removed to ensure the safe unloading of a vehicle. One of the pilots sprinted to the flight deck to re-apply the brakes and prevented the aircraft from continuing to roll off the airfield and down a hill.
And people steal chocks, which is the reason the aircraft registration is sometimes etched onto the chocks.
If there is a slope, the aircraft may roll onto the downhill chocks. Depending on the taxi out direction, it might be difficult to then remove them for departure.