Remember a bare sensor is just that, it is the sensor with filters and cleaning circutry usually removed, and while there may/maynot be Dichrioics/Sealed assembly before the actual sensor, connections to the sensor are being exposed to cleaning materials, solvents, etc. At home, you may have clean windows, but now look at the frames. Is there any dust dirt, or particluate matter settling in there. Now imagine in that frame micro-sized with hundreds of SMT connections exposed, to cleaning, solvent, enviroment, particlute.
Again, who cares if someone enjoys a bare sensor, I certainly don't care, and usually advocate for a full spectrum mod because its the BARE modification that maintains focus, and a sense of security by having a protective glass in front of the sensor.
People who deal with electronics, and professionals who repair and perform modifications advocate glass in front of the sensor. No one here, including me, is saying bare sensors stink or don't perform, what I am saying is that professionals who provide the service advocate for glass in front of the sensor for many reasons, some of which are, protection, lens focus, and accurate repeatable calibration.
I've been cleaning sensors for more than 20 years, for myself and other photgraphers.
If you doubt that scratching a sensor is a problem, please do a google search and see how scratched sensors can get.
Clear Skies !!