I believe that the sole reason is money. Although the software released for the
GBA is fairly bug free, the quality of the majority of games released to date is
extreemly low.
I see no evidence of quality control at all.

Chris B.

> Virtually all console producers follow this route ( I know of none
> that dont ), it allows a level of quality control completely unavailable on
> the pc, one of the reasons that games on the pc dont do so well ( other than
> quake ), the amount of testing that a game goes through is immense ( trust
> me I know ) before approval, how many times has an end user believed his pc
> to be broken due to dodgy software, Nintendo dont want users to think their
> machines are dodgy due to inadaquately tested software.
> The real reason for this policy however is money, The development of
> a top console is extremely expensive, and they actually sell them at very
> low prices when thats taken into consideration, think how much a small lcd
> tv is to buy, add in the relevent computational electronics and you'd be
> hard pressed to match the gba price, never mind the many millions that were
> spent developing/marketing it. In many cases machines have been sold as loss
> leaders, similar to the mobile phone market, with companys using software
> sales to make up the deficit, and eventually lead them into profit.