The house frowns on people taking roulette chips away from the table becasue they are not denominated and it could lead to cheating. You could play at a table one day and have the chips value set to $1 each - take about 20 home - come back a few days later play at the same table with the same color chips and get them set at $25 - then sneak the original 20 chips back in and make a nice little profit. Collectors just want the chips for their collection - but it hard for the house to know your motives....