Tradition has it that there were 2,884 old aikijujitsu techniques. There may have been a countless variety of applications depending on the circumstances, eg. location, opponents.
These numerous techniques were sorted and classifiied into a basic set of 17 which we can use freely in randori practice to improve our skills. In matches we can also develop stamina and courage which is the strong point and aim of the randori practice system.
However, we must not forget about the wide range of kata techniques. For example, there should be a variety of self-defence techniques taught according to when, where and what kind of attack. Randori techniques are of a different type. If we look at the reasons for the development of competitive randori practice we see that it comes from the viewpoint of self-defence techniques without the emphasis on actual fighting. Training in competition style techniques is the fast route to improvement. Intelligent people recognise also that it is very difficult to put kata techniques to practical use even though that is the essence of these techniques.
So, we say that it is desirable to practise both kata and randori side by side. In Shodokan aikido we have well-structured practise system unbiased towards either kata or randori practice. However, students can adjust their practice according to age, ability, etc.