there are only 46,656 different possible dice rolls, that plus with how there are multiply solutions for many of the bigger point possibilities means that the odds of getting 3 '3 pair' rolls in a row aren't nearly as high as you might think.
ok look at it like this: You score ten time for 300 each time, thats 3000 total. the reckless computer only scores three times but scored 1500+ each time, thats 4500 and then a possible -500. So at worst for the computer, it has a 1000 point lead.