Ripping at 4X even though drive is 12X

[autojack]

I have an old TEAC DV-W58E drive which I use for ripping movies. I have it in a USB2 enclosure plugged into my Macbook Pro. The only issue I have with it is that when I rip with MakeMKV, read speed maxes out at 4X or 5M/s. The drive advertises up to 12X DVD read speed, so why can't I rip any faster than this?

[Woodstock]

Advertised read speeds are not applicable to ripping, other than the drive CAN read faster, if the disk is "perfect" and you're reading the part of the disk where the rating was done. This is typically the outer-most portion of the disk, not where movies and such begin.