Does seem a bit odd doesn't it. My 1/4 sockets go down to 3/16 and 4mm. Smallest nut driver is 1/4 but metric set also starts at 4mm. Smallest carb wrench is 5/32. Don't recall anything requiring 1/8 but I'm sure it's out there or they wouldn't have made socket lol. I don't own any but there are a few 1/8 drive sets out there with 1/8 x 1/8 dr sockets. Pretty small. My son uses a lot of 1, 1.5 and 2mm hex drivers in RC hobby which would be similar scale but don't recall coming across 1/8 nuts or bolts before. Believe older Fords used 5.5mm alot in instrument cluster and under dash but that's quite a bit larger than 1/8.