My knowledge of economics is quite limited, but as far as I understand, the "added value" which is taxed by value-added tax refers to the difference in the cost of production and the cost in the store. Since the product has to be processed, packaged, transported etc. the cost will rise because every person in this chain wants a bit of money for themselves. The government then taxes this added value. Correct?
If this is true, then why is there VAT on services? Most of the services are "supplied" directly to the customer. For example, if a hairdresser cuts your hair, there were no intermediate persons in this process and the cost of the hair cutting service didn't rise because of them. If you're a web designer, you make a website and provide it directly to the customer - it doesn't have to be transported etc.
Basically, why would someone have to pay value-added tax if there is no added value?
(This also goes for all goods that are sold directly to the customer - but unlike services, goods can be passed on (the customer can sell the good that he has bought) whereas services can't, so I think that most services should be exempt from VAT).