Essentially what I mean by what I have said is that, for example, I am on a Computer Science degree. At the end of my degree when I start work or start my own business I will be looking for more money that ads would give me.
I currently am in double figures per hour at the moment in my current part time employment so there is no way that I would be able to drop to the wages that ads would give me.
Another example, a web design
website hosting - they wouldn't need the ads cause they could make £25 an hour (at least) by designing web pages - they don't need the few pounds a month the ads provide along with all the stress and hassle with programs like Adsense