You're comparing oil-based and alcohol-based materials when you compare BLO and shellac, generally incompatible materials.
Alcohol and water play together much better than oil and water. Therein is a clue to durability traits.
Agree it's not the most durable finish. The two components are very compatible though and mix easily.
If the only tool you have is a hammer the whole world looks like a nail...
There are literally millions of ways to finish wood. Choosing one of the oldest and worst and mixing it in a difficult way to use with another outdated and poor choice and advocating its use in a place where it will make a difference is funny in a sad way...
You need to look at new tools...
