That's because it was not designed to Interstate Highway standards ~ in fact, it existed BEFORE the internet system absorbed it.
The big money boys in MD already took the money 60 years ago ~ that highway was designed as a money pit that would cut through their property and yield them a vast treasure trove of taxpayer dollars forever.
Because of another MD land boondoggle called "Corridors and Wedges" MD"S Politicians and highway bosses refuse to consider constructing another bridge up the Potomac any closer than Point of Rocks ~ which is way out of the urban area that needs the service.
That is the politicians in MD literally want a BRIDGE TO NOWHERE!
"Maryland Freak State" Is only a small glimpse into the bizarre of MD politics.
Time to ban the term "inter" ~ it has outlived its utility.