Why does 4.3bsd login clear local terminal modes?

[Web Dove]

The 4.3bsd login differs from 4.2 in that it jams the local mode bits to
zero for both normal and remote terminals (4.2 only did that for
remote ones).  What is the point of an easy to maintain gettytab if
login throws the information away?  This is especially a problem with
tcsh which sucks up the terminal modes at startup and resets to them
whenever it has a problem.