DFC Quote:
Small point but I think that you will find that the end of a taxiway is where the taxiway and the runway join i.e. at the physical edge of the runway.
It's no small point to not know where being guilty of a runway incursion is, and the definition you give (join at the physical edge of the runway) is most certainly your own and other misinformed souls when it comes to a taxi limit that doesn't include a runway clearance. I would fail any PPL candidate that didn't know this very very basic and very very vital/safety-related definition.
Taxiway holding positions (holding points) are designated (marked) to ensure that the largest aircraft for which the aerodrome is designed holding at the most adverse angle does not infringe a myriad of obstacle and / or signal critical areas.
You are speaking to why hold lines may be where they are...it doesn't matter to a pilot why they are where they are, but the pilot must know those lines deleniate the taxiway side vs. the runway side. Being hooked on your own erroneous definition (where the pavement joins), or being over-interested in why hold lines perhaps are different distances from the centerline, have you wrapped around the axle, so to speak.
Asking a pilot to hold short of runway(nn) assumes that the pilot knows the design standard of the aerodrome, the aerodrome category, the physical limitations and the signal in space limitations not to mention the wingspan of the aircraft about to roll combined with the pilot's ability to maintain the centerline.
Bit of a big ask!!
It assumes no such thing, and nobody's asking it of you as a pilot. What's asked of you as a pilot is to understand basic pavement markings and obey them, since they are so you can obey the instruction. Only not understanding would lead you to think an instruction for you to "hold short" is as large and convoluted as you're making it out to be.
Hence the reason for holding points (position).
The reason for hold lines is to define taxiway side and the runway side of pavement. Learn this...please. You're confusing yourself. You're trying to build a watch when someone asks you what time it is, except watch-building in this case is a detriment to safety.