Bicycle Mechanics - stuck fork

Through out the years I had to remove the forks on my bikes. Either to make adjustments, renew the grease, or replace a headset. Now almost everytime I did have to remove a fork it did not come off easy. I had to give it a smack. With a hammer(and a piece of wood for damage control). Most times a tap did not do! I had to bop it real good. Now I'm just curious....after all retaining devices are removed what is holding the fork in place. The stem isn't rusted...there is free movement(on the bearings). So is there anyone knowing the reason for this.

If they are threadless headsets, most come with a conical compression ring, installed narrow end down on top of the upper bearing, that centers the steerer in the bearings. If this has been driven in firmly the steerer can be hard to remove. Be sure you remove it.

take a look at the top of the stem, where the compression bolt and cap goes. check to see if its been mushroomed after the attempts of hitting it with a tool. you'll see the metal of the stem start to crush in, causing the top to actually narrow. good luck.