Imagine how different life would be without gravity. Could pinball be played?

Maybe, but it would be a lot like bumper pool.

Imagine how different pinball would be without friction. Could pinball be played?

Sure it could. It would actually make the game faster as you probably imagined. When the ball is hit by the shooter to start the game it has some initial amount of Kinetic Energy. Some of this converts to Gravitational Potential Energy as the ball goes up the inclined playfield. Everything on the playfield that makes the ball go faster (flippers, bumpers and sligshots) gives the ball Kinetic Energy. Shortly after being hit by one of these objects a pinball will develop spin if friction is present. As a result some of the ball's translational kinetic energy is converted to rotational kinetic energy. The result is a reduction in speed of about 20 percent of that in a frictionless, non-rotating ball.

In public you can run into games that seem to play a lot faster than others. Take a close look at the surface of the ball and the playfield. Are they both ultra-shiny or pathetically grimy? Pinball collectors know very well the benefits of using unblemished balls and keeping their playfields waxed to a nice smooth surface. For the player it makes a big difference in the game speed.

For the collector the playfield will experience less wear. Picture a person at the bowling alley preparing to roll a ball down the alley. Notice that when the ball leaves the person's hand it is not necessarily spinning. It may slide a bit before developing its roll. On a pinball game a quick shot to the ball from the flippers, etc. will send the ball across the playfield in much the same way. The ball will initially slide before getting into a spinning mode.

If the ball and playfield are both nice and smooth the ball slides more than it rolls and has a greater speed as a result. The player likes this!

If the ball is rough and sliding across the playfield, it acts just like sandpaper. The collector hates this! Notice on machines that have poor playfield surfaces that most of the wear occurs very near to the flippers, bumpers and slingshots. They usually have badly pitted balls as well.

Faster play increases the likelihood of damage in other ways however. A faster ball is more likely to cause plastic pieces that populate the playfield to crack when they are hit. The collector does not like this! For the collector this can be a two-edged sword.