Sovereign Wealth Funds~Why Are Countries Playing At Investments???

Japan’s ruling Liberal Democratic Party is spearheading the creation of a $100 billion sovereign wealth fund (SWF). That would put them on par with Singapore’s Temasek:
The group of 42 parliamentarians, led by former minister of financial services Yuji Yamamoto, hinted that it will tap into Japan’s $1 trillion-plus foreign reserve trust, $582 billion of which is held in dollars.

{Countries should not have wealth reserves of this magnitude, they should opperate in the best interests of the tax-payer and return surpluses when they are built up......yeah, fat chance I know.}