You must have bought a game at some point in your life. If not, you're in the wrong place. Ask yourself this question: "Why did I buy it?" There are several potential reasons for this, but I'll lay a fairly hefty wager that a good part of the reason was its marketing.
Michael Foster

Long ago, further back than I'm comfortable to admit to remembering, gaming was very much a niche market and advertising was very low-key. You saw a console in the back of your mum's catalogue, and later, if you were a good negotiator, in your Christmas stocking. That was about it. Your mum vaguely knew what they were, having seen a Space Invaders machine on holiday, and, not wanting you frequenting arcades, got you one so you could play for free at home. Much later on you talked her into getting a proper computer. With mother naively agreeing that it could help with your homework, you had another avenue to gaming.

However, videogaming was still almost an underground thing at the start of the home-computer revolution. Consoles like the Atari 2600 were just about starting to advertise, but the Sinclair Spectrum, BBC Micro and so on set their stall out as serious machines. It didn't take programmers long, however, to realise that people really wanted games, and before long names that are still familiar today began producing games. Things were still very much word of mouth, though, and limited to the occasional brochure and advert in the nascent computer press. Needless to say, relatively few games were sold.

The first really major game advertising began when the Sinclair Spectrum and Commodore 64 were firmly entrenched in people's homes. The few games that had sold in relatively large numbers woke people up to the fact that there was some serious money to be made. Ultimate (the ancestor of Rare) put out huge poster campaigns for titles like Sabre Wulf and Underwurlde. People were captivated by how cool the advertising was and immediately assumed the game would be good too. They sold like thermally advantaged confectionery.