Louis Davidson on naming constraints:
It has long been a habit that I name my constraints, and even if it wasn’t useful for database comparisons, it just helps me to see the database structure all that much eaiser. The fact that I as I get more experience writing SQL and about SQL, I have grown to habitually format my code a certain way makes it all the more interesting to me that I had never come across this scenario to not name constraints.
Temp tables are special. There’s another reason to have non-named constraints on temp tables inside stored procedures: it allows for temp table reuse, as shown on slide 21 in this Eddie Wuerch slide deck from SQL Saturday 75 (incidentally, the first SQL Saturday I ever attended).