Yes this is quite common as the cost to do the job is often a lot more than the customer expects and is just easier to say no, a mate who has his own workshop had to replace a number plate on an Audi recently, the bulb was pence but it took him over an hour by the time he had removed the corroded screws and cleaned up the contacts. Total bill was nearly £60 and the owner had a fit.
As has been said brake pipes are often a lot of work, you only need a broken bleed nipple and you need to remove a few rusted parts and it could easily be a few £hundred. I was asked to do the rear brake pipes on a 1998 3 Series BMW, rear axle, fuel tank and exhaust out and I new it was all going to be rusted solid. A garage had quoted her about £1500 + the VAT
, I was suddenly very busy for several weeks and let someone else have the hassle.
You can see why old stuff gets scrapped for what on the surface appears to be a small job.