Why do commercial receiver extensions exist?

[Lincoln7]

Why does the commercial receiver extension exist? Are there cost savings? Easier to manufacture? A miscalculation somewhere along the way? I've never heard any reason(s) before but, without a good one, the fact that they exist in the market seems stupid, limiting owner's stock selection. I suppose it makes it easy to identify the lower quality AR's...

[rob_s]

I believe it has to do with reverse engineering the system, and the reduced cost of machining threads vs. rolling them into the tube.

[Frens]

as stupid as commercial carry handles or non standard handguards cap..

[rob_s]

Commercial carry handle is a similar thing. Manufacturers already had front sight bases for rifles and so rather than change to a carbine, F-, height FSB they simply lowered the carry handle to match.

IMO the HBAR is the same as well. They had two diameter reference points they had to meet; barrel extension and front sight base. Cheaper to make long, fat barrels that step down where needed than to machine the A2 profile. HBAR was born and the "you need a heavy barrel for accuracy" nonsense was foisted on us.