They do, if the lawnmower believes "more trademarks good" (and which corporation doesn't?), and trademarks must be actively used and defended to be kept.
Like all machines in the real world, the Oracle machine intelligence is limited - it can't process every single thing to infinite detail. "More trademarks good" and "trademarks must be actively used and defended to be kept" are heuristics and explain this well if you tack on an "on average" to the former.
