Why do I do this every day?

There is a painted fence on the road from Oxford to London - I think it's on the M40 - which says "Why do I do this every day? NO WAR" - sometimes in different colours. At the moment, it's white letters on a green background. I always thought this was protest graffiti: the "NO WAR" stood out for me because there are similar daubings on the wall beside the church on Jackdaw Lane, the access road to the Iffley Road sports ground. I thought the question meant, "Why do I keep coming back to repaint this sign every day?" I realized today, however, that it could be - and probably is - intended for the commuters who travel to London to work every day. The "I" I always thought was the soliloquizing voice of the fence-painter, coming back in the middle of the night to redo his protest. It's specially angled for London-bound drivers to see at the bottom of a small enclave of trees. I wonder why I always thought of it from the lone artist's point of view, rather than the wider, more universal, audience's.