Perpetual calendars are a bad idea because of skipping special days. How long until the next Thursday? It depends on if it is February or a leap year. Think of how complicated the logic will be to calculate the day of the week.

The point of weeks is to have consistent cycle that can organize life. Also, why is it advantage to have the same day of week for same day of year? I suspect most people would prefer that their birthday wander around instead of always on Thursday. Calendars solved the problem of figuring out the day of week, and computers make it even easier.