Notice Board Spamming

Those who live in Chennai would have definitely noticed such notice boards in front of every house / apartment. During the last 3 / 4 years, advertisers seem to have taken keen interest in displaying such "No entry for visitor vehicles" / "No entry for salesmen" boards in residential localities. Although one such board is more than enough for each apartment / house, one could normally notice 2 - 4 boards in each gate. To me, these look like the new age wall posters. The real intent of the advertisers is revealed when one realizes that the advertisers name often occupies 50 - 75% of the space in the notice board and the genuine message occupies only the remaining 25 - 50%. Why can't advertisers stop putting such notice boards when they see that one such board is already present in the gate? 3 - 4 boards is definitely an overkill.