Its more effective though, Blur having a political
slant (albeit a politically correct one) for 3
reasons:
 
A) More people have heard of Blur than some
body like Discharge so therefore the message
is heard by more people.
B) Blur arent a relentless political band. The
majority of their songs say nothing, and there
fore the message sticks out more. The problem
with a band like Rage Against The Machine is
that every song is political, too much of it
in a preachy way doesnt work. Even the
greatest comedian of our time, Bill Hicks, used
dick jokes to give people a bit of variety, a spoon
full of sugar helps the medicine go down.
C) They are releasing singles with political
messages or videos. More people will hear them
because of the radio or MTV. If all of the political
stuff is only on the album, only your fans will
hear it. Preaching to the converted.