You can register with the state, but the people standing outside your grocery store with registration forms are not the same people. They work for particular politcal groups. By law they are suppose to file all the forms with the state, but companies Nathan Sproul has been in volved with (such as is the case here) has had a history stretching back over a decade of trashing even burning registration forms that were filled out by non-republicans.
When they are cuaght the RNC makes a public firing of the company then Sproul changes the company name and the RNC quietly hires them again.... wash, rinse, repeat...
In this story they caught a supervisor throw 8 forms in a dumpster. Those forms have since been filed, but how many did he trash before this? The only way to be sure your registration gets to the state is to do it yourself. Take sick day, google where the closest place to officially register is, and go. Otherwise it is entirely possible you will show up at the polls after standing around for 2-6 hours waiting only to hear "I'm sorry. You're not listed on the states voting rolls."