USB sensors are more expensive and need an USB hub (which raises the price, what's the point then?). Not to mention most sensors (humidity or CO2 for example,

USB sensors are more expensive and need an USB hub (which raises the price, what's the point then?). Not to mention most sensors (humidity or CO2 for example, or even just a simple potentiometer) are not USB (and for a good reason, I don't want/need USB chips and connectors in each one of my sensors). Example applications I use Pi for: automated irrigation, custom digital musical instruments.