Because I'm making a specific calculation, from a specific viewpoint. What I'm telling you is what happens when an employer decides to give you 1 euro of their money, how much you get out of that, in terms of what you can give someone else for a good or service, in the (oversimplified) common case. Given that perspective, I feel my calculation is, barring some oversimplifications, correct.
To be exact at the beginning of the calculation I'm calculating euros that your employer spends on you. At the end of the calculation is money you have given to someone else for a good or service that they can actually use for something.
If you want to look at it from an employee's perspective, you're right taxes would look different. In fact, on your "bruto" pay you'll pay income tax, which will come out at around 45%-50% if you're on something around 50k euros/year bruto. And yes, add 14% because of the 13.92 (well, keep in mind that it'll be taxed at the 50% tax rate, and there are additional taxes levied on top of that 50% on that amount, so frankly it'd be safer to assume you get 5-6% on top of your bruto pay actually deposited in your bank account).
I feel like this is a way the government masks how high taxes are, but of course you can look at it however you want. I guarantee, however, that employers budget for your pay in terms of euros they need to pay to anyone to have you on the payroll, and I guarantee that when someone decides on the price to sell you something, they'll consider VAT to not be part of the money they get.
