REDUNDANT AND ANACHRONISTIC
Bicameral legislatures are anachronisms. Their origins lie with the snobbery of English nobles in the late 13th century, who were loathe to sit alongside the uncouth lower clergy and others called to advise King Edward. In our own commonwealth, it stemmed from the corporate structure of the Colonial Massachusetts Bay Company, which had both a board of magistrates and a committee of members. The US federal system — replacing a unicameral legislature under the Articles of Confederation — was born of the compromise between small states (which received equal representation in one chamber) and large states (which got proportional representation in the other).
None of that is relevant to the Bay State today. Nor are arguments stemming from different functions of the chambers. In Massachusetts, neither the House nor Senate has significant special powers or authority, such as confirming appointments.
So why exactly does the state have two redundant legislatures? There are two claims: to ensure local representation; and to serve as a check against rash lawmaking.
There is certainly something to be said for a representative on Beacon Hill responsible to 40,000 people, rather than 160,000. But given their near-uselessness in the current system, most state representatives have become little more than constituent-services advocates.
Impotent to affect actual lawmaking, most reps earn re-election by trading in fealty to leadership for scraps of district funding, and by begging state agencies to help a constituent by fast-tracking a permit or hiring a relative.
In any event, a unicameral legislature can be as local as a bicameral one. The Senate could be expanded to 60 or 80 members.
There is likewise something to be said for a second body to slam the brakes on ill-considered lawmaking. But that argument is undercut by the fact that the most significant and far-reaching acts of the legislature — amending the state constitution — are conducted in unicameral fashion. All 200 legislators meet for constitutional conventions as one body, and take a single vote together. If it's good enough for the state constitution, why is it too rash for the general laws?