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.