Some interesting reasons!
I would add that with the cost of the part and the work required to install (I've only looked at the ICS instructions, but i'm assuming most GB's need some fettling work to fit), would make the total cost (parts, + labour) a little on the pricey side or just unprofitable.
Personally I love mine, only use a few of the features AB, pre-cocking/cycle detection (for snappy trigger) and rate of fire adjustment (saves on ammo dropping the RoF down a bit), but well worth it imo.
However I will say there support is rubbish. I had a simple problem recently with mine. Has been working fine for years, but I missed the step in the instruction to remove part of the ICS gearbox latch, finally that bit me = dead plastic pea shooter, quick look and I've knocked a component off one of the boards. Dropped them an email for help, reply I got was 'that's not covered by warranty', email parts address (no $h!t I'd said I was after help to identify the part or was replacement of just the affected board available). Must be a fairly common failure and something they could have very simply advised to fix, given me a price for a replacement board or just told me what the part was..... Thankfully easy enough to identify the capacitor via pictures on the 'net and a 2p part from CPC, dab of solder and back up and running. No thanks to there support though... not what you expect from a product priced like that though!.
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