You don't HAVE to for personal consumption. Some people live in states where you have to grade eggs to sell them. You can also use weight while incubating eggs to determine development.
It's very useful to know the standard weights for common egg sizes and weigh eggs you are baking with. I had a few recipes come out odd because I guessed how many larger or smaller than usual of my eggs to use or how many bantam eggs might equal a standard large egg. For that purpose though you don't need a specific scale. Any postal scale will work.
I was worried about not knowing the sizes of my eggs when baking since I don't have a scale. Go to http://www.aeb.org/LearnMore/EggFacts.htm Go down to size equivalents. It has helped alot with my baked goods coming out right.
I never have been able to understand why egg scales are so pricey...I mean I can see the antiquers being on up there but modern ones are still $25-$35 each....
You would think that an inexpensive plastic scale could be found but there just aren't that many sources around and they all seem to be of the same manufacturers.....
Probably the result of supply/demand and a soft demand for the new ones.....
I've got my mom looking for one or two when she attends the antique auctions up in Shipshewana and Wisconsin....hope she's lucky....
Ran across this old thread while I was looking for info about egg scales, and had a brainstorm. I have a Weight Watchers electronic scale that weighs to the 1/10th of an ounce. It will work GREAT for weighing eggs, fits in a drawer, and doesn't have the ugly rooster silhouette! I looked on eBay and there are a lot of small electronic scales out there for around $25. Or just go to a WW center and buy one!