I never said they all had them on the front, I said they were readily accessible, meaning you can access them without taking anything apart. However, some of the older PC monitors (CTX comes to mind) didn't have a pot at all for horizontal size; the only way to adjust it was with a plastic Allen wrench to turn the horizontal width coil on the chassis (you have to remove the monitor's housing to do this). This also applies to most older TVs and most older arcade monitors.
Standard resolution CRT TVs were fully optimized for an NTSC signal at the factory. Since they are only ever used with NTSC or NTSC-like signals at home, there is no need for the end user to ever have to adjust raster size and position, unless something goes terribly wrong with the TV. That's why most of them don't even have readily accessible raster size/position adjustment controls.
The two differences between a 15 kKz CRT TV and a 15 kKz CRT arcade monitor are:
1. The arcade monitor has no TV tuner
2. The arcade monitor has RGB input
All of the adjustment controls on an arcade monitor are readily accessible because they have an open frame; i.e., they are not encased in a plastic or wood housing like TVs are. Also, they have better picture quality than TVs because of the RGB input (RGB is the purest analog video signal possible), and because they are usually displaying progressive scan video (i.e., not interlaced). There are a few exceptions, like Nintendo's Popeye, and some of the Bally Midway games like Tapper, which are interlaced. But, any CRT monitor or TV can display interlaced or progressive video, as long as it falls within its sync range (which is ~15 kHz for standard resolution arcade monitors and TVs), so those oddball interlaced arcade games used ordinary arcade monitors.