Quality control...
Let's say that maybe it was MORE cost effective to ship without the lte cards that could have been defective, have them proven and made more reliable, and then installed and shipped back to you. Also to prevent angry consumers from trying to sue. Id rather have ppl angry for waiting than lawsuits pile up for selling a defective product.
Also every droid manufacturer are in an arms race not only to compete with Apple, but also each other. Lack of standardized hardware leads to many things...hence why OS updates are few and far between.
Take the fact that the Tbolt has been delayed, what 6 times? HTC also seems to suffer from rushing products, and maybe Verizon is saying (aside from trying to keep the VeriPhone sales competitive) to HTC that Hey this isnt right, hey customers will take this back because of x, y and z, hey we buy these subsidized in bulk, fix it or we wont sell.
Quite a lot of factors go into the decision to release a product; timing, price point, competitive models, possible hard and software defects, etc. Motorola probably had their hand forced to release the Xoom with missing features to try and cut out not only the iPad2 but other dual core droid tablets.