
The answer is yes, it really really is. And I will give you a short answer as to why and then if you want to learn more you can keep reading.
Short answer: It helps with the accuracy of your knitting and helps to ensure a successful product.
For the long answer, keep reading.
Swatching is a technique used in lots of different industries, not just knitting.
Other terms you might recognise which is very similar to swatching are; prototyping, modelling, toile.
All of these things are practice versions of the thing you want to make, by making a practice piece first, you are more likely to recognise any flaws, find ways to work better, use material more efficiently etc.
In knitting, making a practice piece first is really difficult and massively time consuming! So let’s think about what you need to know in order to knit a successful product to the SIZE that you want.

1.       You need to know the knitting gauge; this will be in the pattern notes along with the needle size and recommended materials. This gauge tells you how many stitches and rows create a certain sized square.
2.       You need to know what needles and materials you need.
That’s it. That is all you need to know but it is a HUGE part of the pattern!
So, to help us make sure that we are knitting to the right gauge and that we have the right tools and materials to do this, we knit a swatch first. We knit the amount of stitches and rows of the knitting gauge given to us. If your swatch ends up being the same size as the gauge, then you know you have done the right thing and that your product should be the right size. If your square isn’t quite right, then it means that you might need a different size of needles or a different thickness of yarn.
So, this is why knitting a swatch is so important. It is the practice piece of your pattern

before you begin knitting it. Having the opportunity to spot errors in your tension (how tight or how loose your stitches are) is really helpful and can help to reduce a very big error of knitting something in the wrong size which trust me, we have all done!
I really hope you found that helpful and as always, happy knitting