It wasn't. Since about 1972 (IIRC), there has been an EPA-mandated ceiling on the total number of parking spaces allowed within the City of Boston. They've since relaxed some of the rules for certain off-street developments, but the total number of on-street parking spaces and "public" garage spaces has remained stagnant. It's treated as a zero sum gain by the EPA - if the City does street improvements that result in fewer spaces in one place, they are allowed to replicate the spaces they lose elsewhere.
Did only Boston have such a restriction or was such also applied to other cities? In the near-26 years I've lived in the Philly area; there has definitely been an increased number of overall parking spaces in Philadelphia (mostly in the form of above or underground garages).
Yeah, I understand that the cost of living skyrocketed in the 80s because of the development along the Route 128 corridor. I'm sure that Carla's nonexistent house near Logan (if such a thing existed) would be worth six-figures in 2014.
The episode when she moves in (5th season, early 1987) took place right when real estate prices in the Greater Boston area were skyrocketing. Cliff's
"It's a sellers' market" quote during the episode gives reference to what real estate prices, as a whole, were doing at the time.
The cost of living in Boston is a pain in the ass though and I say that as someone who is actively looking for apartments in the area.
Such has largely been an issue since the mid-to-late 80s. I remember one local magazine article (it was either from
Boston Magazine or
Marblehead Magazine) that had an opening headline that read
"Where Will Our Children Live?" that commented about the soaring real estate prices effect on young adults leaving their parents' homes (due to marriage, job, whatever). I.e. more and more of them were forced to move further away.
Fast forward to about the mid 2000s and another article (this time from the
Boston Herald) covered the exodus of young adults (ones that actually contribute to the tax base) from the state due to high real estate prices (including apartment rents).
Not much has changed in that (high real estate prices & rents) regard except that it's now expanded well beyond the I-495 corridor now.