When wrench sets skip sizes, how do they decide which to skip?

[JR 42]

I've bought skippy sets before, and filled in with equivalent wrenches... My budget's too limited for OCD.

What I want to know, is why sets like these are offered-

http://www.protoindustrial.com/en/i...bination-ASD-Wrench-Set---12-Point-7MM-32MM-/

What industry only uses even- number metric sizes plus 7mm and 29mm? Armstrong had something similar also.

 

[dnschmidt]

This was a constant source of tension between myself and TOPTUL. They would seldom include 13, 15 and 18mm wrenches and sockets in their sets perhaps believing that American cars didn't exist in this world. Kept beating on them to change but naturally they never did. They make a set of zero offset super long box end wrenches that I could have sold 50 sets of except for the fact that it didn't include any of the previously mentioned sizes. The wrenches themselves were beautiful. Being out of that game for a couple of years now I constantly wonder why I put up with their **** for so long.

 

[Hobby_Man22]

9 and 11mm are rarely used?

16mm and 18mm is used on oil drain hoses. Ive used 11mm here and there when the 10mm was lost

 

[Sumboodie]

I own 3 asian cars and a 'half asian' GM. Never use anything smaller than 8, nor 9, 11, 15, 16, 20, 22. There's a few standard size that are almost always 3/8 or 1/2 on my nissans though I can't think of anything offhand right now. 5/8 & 16mm are close enough that most spark plug sockets just have both sizes printed on them so it won't matter.

Some guys (I think Chrysler) every other fastener is a 15mm. Other sizes I swear it's only chosen because so few people have the socket or wrench so it's kind of a cheap way of making a security socket. 4mm is like that for some small electronics. A lot of sizes stop at 4.5mm or 6mm and don't go smaller.

Now I won't say that 'if you are missing a size you aren't a real man' or any foolishness like that but if you are a home hobbyist, you know what you personally are working on, you can get a set that skips the sizes you don't need. If you're satisfied with having only what you need, great. if you're like me and have to get every size, great. But the sets that skip sizes are usually because they can sell you an 'incomplete' set for less money, plain and simple.

Early emission junk on 70s-80s often used metric. Everything else was normal.
Could tear apart a square body Chevy with 3 or 4 wrenches.