The safest way to start or finish your session will always be with the help of a competent assistant (i.e. a well trainer kitesurfer who knows how to safely handle a kite and understands/uses hand signals).
Yes it's good have the skills to self-launch and self-land but not essential. Most kiters (especially beginners/intermediate) won't go out by themselves anyhow and will only kite when many other kiters are present which is the safe thing to do and also ensures there will always be people on the beach to help out.
Self-launching
The problem with self-launching is that
no matter the technique used it's NOT a beginner skill and therefore it would be irresponsible for an instructor teach this at the early stages of any beginner's progression. Most students will stop taking lessons as soon as they are able to ride a bit and therefore instructors very rarely get a chance to teach self-launching skills.
The other problem is that metro kite spots are often very busy and that failed self-launching / self-landing can easily end up hurting other people, kiters, damaging your gear etc. As as said above, always safest to use assisted launching / landing.
Another problem with self-launching is that it's often poorly executed and a lot of kiters don't understand the risks involved and also don't have the correct safety reflexes to react when things don't go as planned.
Self-launching should be learned in underpowered situations with a small kite, short lines...then gradually practiced in stronger winds.
Self-landing
Self-landing on the other hand can be a beginner skill that can be learned in the very first lesson if done by activating the chicken loop QR, fully flagging out the kite and following the safety line hand-over-hand until the kite gets recovered as per the video here:
www.kitebud.com.au/kitesurfing-online-courses/kitesurfing-safety-systems/Unfortunately this super simple and super safe beginner skill is rarely taught during lessons as it's not part of any kitesurfing instructor course that I've ever seen.
The main problem with self-landing is that 99% of kitesurfers who self-land are doing this while still being hooked-in which is extremely dangerous. Without a plan-B in case of a failed self-land kiters get dragged into the power zone, can easily get hurt, injure others downwind, damage gear, etc.
Christian - KiteBud