A lot of woodworkers take that fact that their timber is square for granted. You buy square timber (often called PAR - planed all round) from a timber merchant and off you go.
Or, if you are more adventurous, you buy rough sawn boards from a timber merchant and then cut it to size and square it up your self. For most people this involves the use of a planer/thicknesser, which is a labour saving machine that shaves your timber to the correct size and makes it all nice and square so you can start work with it.
The problem with a planer thicknesser is that a decent machine would take up most of my workshop space, and they require a good dust extraction system (another big machine). They are also very noisy and like all woodworking machines, reward a moments lack of concentration with a ruined piece of wood, or sometimes a serious injury.
I long ago learned that hand tools give you a degree of control over what you are doing that a machine cannot. Once you've started a piece of wood on its journey through a thicknessing machine, there is no going back if you've got your measurements wrong. You're committed to the mistake. It can be a costly and frustrating process sometimes, and actually rarely saves much time.
Machinery for woodwork is labour saving - it often doesn't save any time after you've set the machine up, emptied the extractors, etc. Machines just save you the actual work part of the job - the labour. I actually quite enjoy the labour aspect of work. It keeps me fit and strong. It doesn't produce plumes of dust that need extraction, dust masks, eye protection, etc. It does produce beautiful shavings that fall on the floor ready for me to sweep up. And if you're not mass producing the same thing every day, hand tools give you a flexibility and speed to change between jobs that machines can't. Most importantly it trains the skills needed to be able to process and prepare timber accurately and quickly without the need for expensive machinery.
Once my timber is planed, it's checked with an engineers square in front of a light in order to ensure it is flat and square. When it's right, it's very satisfying.
Don't get me wrong, I have some woodworking machinery, and I use it. But sometimes I am reminded that the simplest, quickest, cheapest and most satisfying way to do things is the old-fashioned way, with old fashioned hand tools. After spending an evening wondering who's machinery would be capable of processing the stack of 70mm thick oak boards in the workshop, the relief that the whole lot could be processed by me in a morning without any stress and the noise of machinery was a pleasant reminder that reliance on machinery to do basic work isn't always the easiest solution.