I run a local repair shop for tablets and phones. Every single Nexus 7 Tablet with a cracked glass I've seen doesn't have a working digitizer. I don't know if its just the design of the digitizer or poor quality parts or what. I've seen iPhones come in so crushed that literally every square inch of the glass is just chunked up and tiny bits. Digitizer still works fine.
Unfortunately, the replacement parts to replace the screen assembly are about $150 to buy the parts. and for about $249 you can buy a new tablet and just replace it with a new one with a warranty. Every one I have had bring me a cracked one has decided to just replace the tablet. After the cost of the parts and then I have to charge some labor its just not worth it. You could certainly buy the parts and do the repair yourself for cheaper. So its an option. But usually paying someone else will cost you almost the cost to replace it.
Hope this helps!