Isn't 10% of 2 Million, 200,000 (rather than 20,000 which is 1% of 2 million) ? Perhaps you meant 1% rather than 10%. Or perhaps I just misread/misinterpreted your post.
Would one possible reason to refuse client betting be to avoid undesired line movement for personal bets ? Perhaps knowledgeable sports bettors can chime in on this supposition.