So? This store sells to other people besides UK residents, and the laws might not be the same...
From the Revenue and Customs site: "Products advertised in outlets, magazines, on the internet, or shown in catalogues, price lists and other literature may be aimed at the consumer, businesses, or both. If they're only meant for the general public, they'll show you a price including VAT. This is a legal requirement."
I think that you will find that, just as vat is chargable for products sold in the EU/UK even though the seller is not EU based and sells to other countries too, that you need to comply with the laws of the countries that sales are made in. VAT is chargable on products sold to customers in the UK because they are deemed to have been sold in the UK. For the same reason the prices should include VAT for products sold in the UK (and EU for that matter).
For those of us making purchases in the UK there is a separate shop anyway. It should be relatively easy to add the VAT to the price of the game as shown - and then break it down in the bill as would normally occur for sales with vat receipts in the UK.
For the same reasons, if I ran an internet company in the UK but say selling in the USA, I would need to comply with US sales laws and taxes. Just as I am always surprised by sales tax being added to prices for things I buy when I visit the US, people in the UK will be surprised if taxes are not included.