OK, I'll bite - why is a Nespresso not an espresso? The water is under pressure, and it produces a crema - as far as I'm aware these are the two critical criteria for deciding if a coffee is an espresso or not...

If you want to get pedantic, I think a Nespresso would fail the Istituto Nazionale Espresso Italiano standard - espressoitaliano.org :)

But really I disqualify it because Nespresso simply does not look or taste like an espresso. The crema is always a bit pale and it lacks in concentration of suspended and dissolved solids. They later being important if you want to make a milk based drink that tastes of coffee.

The brew ratio is not within the commonly accepted range of espresso.

Perhaps Nespresso means "Not Espresso"