Everyone like to bowl good and it exciting to shoot high games and series. However, we should not fool ourselves into thinking that we are good bowlers when we do this on house shots with todays souped up balls.
As a lefty, when I miss a little right, or hit the ball a little hard, or let up speed, I might leave a 6 pin but have to really throw one bad to go brooklyn or nose dive. If I miss out (left), or not hit it, or throw the ball a little harder, the ball may scream back and strike, I may leave a weak 7 or throw one really bad and leave a three pin. All of these bad mistake can leave me with an easy spare to shoot. Therefore, if I make my spares, I have a chance to throw enough strike to shoot 210-230.
Now, lets go to the PBA pattern C. Every mistake you make will be really critical. Miss right, hit it too hard, or let up speed, you may cross over and not even touch the head pin or you nose dive and leave a Big 4. Miss left, and you may take out 3 on the left, washout or get enough of the head pin and leave a 3-7-9 (2-8-10 for the righties). You'll shoot at 6 and 7 pins spares all day long if you miss and you have to be throwing the ball really good to string strikes. It's pretty easy to be in the 170-190 range in a hurry.
I played Tennis years ago and we use wooden rackets that had a sweet spot the size of a quarter. If you missed the sweet spot, your accuracy and power was way off. Nowdays, they use these rackets the size of a bread basket and have the sweet spot the size of a basketball, allowing for many miss hits. If Andy Roddick was to play with one of those old rackets, he's miss hit all day long and wouldn't have close to the power he's used to.
The same way with us, if we play on house shots all the time, we have no idea how bad things could be if they take our shot away.
Enjoy the walls people, don't fool yourself, just have fun and throw your strings. If you wish to take your game to a different level. Learn to play the whole lane, every angle, and learn to repeat every shot.