Some things Erik did Charles ignored for the sake of keeping Erik around. Take Erik's approach to public transport: it would stop when and where he wanted and it was up to Charles to prevent mass hysteria. If Charles ever questioned Erik's inability to wait 10 minutes for the next bus, Erik simply pointed out that Charles would arrive earlier too.
Once Erik stopped a bus randomly as they walked, for which Charles berated him, but as they went on he saw the little girl scurry to the pavement before the bus restarted.
That weekend he bought Erik the Mercedes.