The problem with those syndicated formats is that they are locked into one-hour program blocks, which prevents playing long works, such as many symphonies. You won’t hear a complete Beethoven’s 9th Symphony, for example.
There are also internal breaks. Classical 24 has two 60 second floating avails between :06 and :59 after the hour that can be locally filled (only one break during overnights.) There are also hard times at :59 and :00 which are options for TOHID and local announcements, and an optional five minute block :01-06 that can be used for news or other local material. So a lot of constrictions for longer musical works.