Thanks @tejing, good to know how it is working for others.
More details: I’m running Gnome and using Gnome Terminal. My understanding is that this combination will not source /etc/profile at any point, and this is by (Gnome’s) design. See Initiatives/Wayland/SessionStart - GNOME Wiki!. Gnome Terminal doesn’t start login shells by default (although this is an option). Apparently environment.d is the new hotness for setting up default environment variables.
Some other possibly related discussions: