if you were to take a .22LR and make it a centerfire would it be more powerful just because it's centerfire? If not then why not make more calibers in rimfire? it would certainly be cheaper than centerfire.

You can't reload a rimfire (easily).

Quoted: You can't reload a rimfire (easily).

+1

Quoted: No, it would not be more powerful.  However, centerfire is more reliable on ignition.  Rimfire rounds are primed by putting a drop of primer compound into the base of the cartridge, then spinning the cartridge and using centrifigal force to pull it into the rim.  Sometimes this does not happen evenly leading to duds.  I have had rimfire rounds that have failed to go off with good firing pin strike.  Take it out, turn it over, and it fires fine.  While most high quality .22lr is reliable, the same cannot be said of the bulk stuff when considering for defensive use.

well I certainly learned something today!

Quoted: No, it would not be more powerful.  However, centerfire is more reliable on ignition.  Rimfire rounds are primed by putting a drop of primer compound into the base of the cartridge, then spinning the cartridge and using centrifigal force to pull it into the rim.  Sometimes this does not happen evenly leading to duds.  I have had rimfire rounds that have failed to go off with good firing pin strike.  Take it out, turn it over, and it fires fine.  While most high quality .22lr is reliable, the same cannot be said of the bulk stuff when considering for defensive use.

Shotar:
Thanks I didn't know that. So a centerfire isn't necessesarily more powerful but it's more reliable.  I guess we all learned something today. Thanks!

One thing you have to keep in mind is that rimfire cartridges have to have brass soft enough for the rim to be crushed by the firing pin.  This means they just can't contain the pressures  that can be run in a centerfire cartridge.  The original cartridge for the forerunner of the Winchester, the Henry, used a .44 caliber rimfire.  But centerfire quickly took over for a number of reasons, including the ability to be reloaded and to contain higher pressures.

A .22 Long Rifle runs about 24,000 CUP, a .223 round runs about 55,000.

ETA:  CUP is copper units of pressure, somewhat roughly equivalent to PSI, but not exactly.

I addition to what's been said already, you also cannot go the other way (scaling the rimfire cartridge up) without problems.  Before the turn of the last century, rimfire cartridges were made in calibers up to around .44 cal.  These things worked reasonably well with low pressure black powder propellants, but when the switch was made to smokeless propellants, the rimfire case no longer had the strength to hold the pressures.  Remember, the rimfire case is essentially the same thickness throughout all of its dimensions.  It doesn't have the thickened case head and web of the centerfire cartridge.
Despite its limitations, the rimfire cartridge case is IMO one of the most significant developments of the nineteenth century.  Basically, with the invention of the .22 cal. rimfire in the 1850s, the problem of how to create a cartridge (bullet, propellant, casing, and primer) all as one unit was solved.  This led directly to the creation of much more sophisticated, "practical" repeating firearms and dramatically boosted the firepower potential of firearms.  The centerfire cartridge is really just a refinement of, and logical next step in, the rimfire concept.