Granted, this tends to happen on free patterns, so you would think I shouldn't complain. However, as someone who also has developed free patterns, I know how easy it is to get and list the gauge for most patterns. Yardage missing? Sure, that's pretty hard to guess at and you need a ounce scale to properly calculate it (and I know I don't own one of those). Gauge? No excuse. None. I behove anyone who's releasing a pattern to the world to give the gauge, and here's why (and why it shouldn't be an issue):
- It allows the user of your pattern to make sure they'll get the same product you did. People knit and crochet differently and have different tension. That means while you got an adult sized hat using size 6 needles, someone who knits/crochets tighter than you could end up with a child sized hat following the same instructions. If you don't give a gauge, there's no way for the user to check to make sure they're going to get that adult hat without following your pattern and ending up with disastrous results.
- It allows to user to adjust the pattern themselves. Sure, if it's a free pattern, you could be lazy and only give one size. That's ok; we understand. But when you do that and don't give a gauge, the user will be left either wondering what to do to adjust for, say, using a different brand of yarn (which will affect gauge even if the same weight) or how to adjust for their particular size (after all, why go through all the work of making it if it's not going to fit right?). A stubborn yarn crafter like me may reverse-engineer it, but that's asking a lot from your users just to make sure they get what the picture shows.
- It's not hard to calculate and list. This is the crux of the above. Sure, there are many useful details that can be in patterns, but some of them require special equipment or some major calculations. I understand if you don't want to go through that. But gauge is not one of them. You did a swatch and/or created the item you wrote a pattern for, right? You may have winged it and wrote the pattern later, but that means you have the finished item. Get a ruler out and measure your gauge. If you're simply writing the pattern, you either got the gauge from a swatch or you're using a set gauge to calculate out your pattern. Show you work; list that gauge! There is no excuse not to know that information. List it on the damn pattern.