When each of these roadways was planned, designed and constructed, agreements were reached with the communities about large trucks that would not be permitted for reasons of safety, noise and a general recognition of community livability.
 
MD 702 is nearly all residential.  MD 43 was not to serve as a bypass to the Beltway, nor was it intended to serve the White Marsh Mall from the west.  Trucks may use parts of it to gain access to US 1 (Belair Road) from the west, but the residential areas to the east of US 1 large trucks are restricted.

This is a good reminder that not all answers can be discerned  simply from driving on a road. Motorists are not in a sposition to know the history  and background  of the negotiations that got the road built in the first place. What looks like sheer  stupidity might have been the only way to get something done. (The intersection of Route 100 and U.S. 29 is another example. The goofy interchange design was forced by the need to protect an  historic property.)
 

Unfortunately there's no room on road signs for complex explanations of the the back story of highway construction. Maybe highway gurus could come up wiith a pithy, universally recognized  symbol that conveys the message: "Trust us, there's a reason for this nonsense.")

And, no, as important as it is to get the beer to its destination, the state can't go abrogating its deals with local communities.