These were designed to fit into the limited space of the TLR 22. To do so the size of the cells need to be smaller hence the lower capacity. Now this isn't a bad thing since the racing heats and qualifiers are well under the battery's limit, 5 or 6 minutes being the average heat. Even using a mod motor I doubt you would ever drain more than 2A in a heat so any worry of dropped voltage wouldn't be of any concern.
Add to that the advantage of being able to move the battery fore and aft to tune the chassis is worth the lower weight and lower capacity. Why waste space, weight and cost for capacity that actually hinders you?