There are several reasons why temporary repairs are made.
- in wet or icy conditions a permanent repair wouldn't actually work - the hot bitumen would instantly cool before adequate compaction could be achieved and the ice or water would also prevent the repair bonding to the road
- permanent repairs take more time and, depending on their location, may require a road closure or temporary traffic lights to be brought in
- potholes, or a series of them, may be symptomatic of a more general, underlying problem on the stretch of road - this requires further investigation and potential resurfacing of an entire road section, and is a larger job and so can't be done immediately