There are bound to be interdependencies in the system that are just revealing themselves.
Since it is not a "total government shutdown" most people seem to think it can be "business as usual." However, as this continues to drag along, there are bound to be impacts not envisioned by the mere shuttering of individual agencies.
Such as Transportation Officials Worry About Long-Term Effects and people who have marketable skills will say, "Enough of this, I'm out of here."
Think about the processing of disaster recovery paperwork. Never a fast process and now getting close to being an additional month of backlog.
We will be seeing more stories on how a shut down of program X is impacting another totally separate program Y.
Congress will be getting an earful from their constituents as they travel back home for another weekend.
Holding up the tax return refunds would have been the type of issue/impact that would brought a hue and cry from many circles. Still today, the pain is not enough to budge leaders from their entrenched positions.