The tape is actually a tell-tale.
All around an aircraft that is in the care of groundcrew there will be bungs, plugs, locks, blanks etc that must be removed before flight. Two small, but none the less vital plugs and covers are used to prevent insects or moisture getting into the aircraft pressure instrument sensor - altimeter and air speed indicator for instance.
These are generally small and hard to see. They have commensurately large red flags with scotch brite tape. SLF will rarely see these as aircraft on the ramp will have them removed. You might see them on the servicing ramps on the other side of an airfield.
The door handle tape is used in the same way.