Because USB is not a multi-tap network. It's a point-to-point between host and peripheral, or host and host pretending to be a peripheral (OTG mode).

That USB dongle was bodged on to the USB port D+/D- pins going to the tablet's SOC. If you then connect a PC to that port, you have two hosts (SOC & PC), and one peripheral on the same pair of data lines. No bueno.

I can't believe the bodge job inside that tablet. It looks like the prototype became the final product.