Now, this is by no means an “official” answer. This is my own opinion after having lived in Israel for many years and having served in the IDF, sometimes attached to some of those SOF units.
Israel is a small country with a population of roughly 3+ million that can serve in the IDF both as active duty or as a reservist. The IDF is not a big military and has historically been composed of small units that can perform very specific tasks and be “regular” infantry when needed as well. Like in the Marines, every IDF soldier is a rifleman.
Israel is surrounded by hostile countries and enemies that do not share the same restrictions the IDF has. These enemies do not care about collateral damage, they do not care about using children, women and elderly people to perform acts of terror. Their tactics and techniques are constantly evolving, changing and new threats are often introduced. Israel has to adapt, and do it fast,
On top of that, most operations are conducted on urban terrain or locations where town and cities are under constant threat – i.e. our own back door. Israel doesn’t fight on a far-away land. Israel fight right in her own backyard and often inside her house. Everyone serves. Everyone gives. That’s the reality of the land.
Because of the very small number of soldiers on active duty at any given time, the warfare landscape, and the tradition of special operations started by the Haganah and other early IDF precursor organizations, the IDF prefers to create new units that can handle a very specific threat the best way possible and not rely on bigger, heavier, slower to move regular units.
For example, when dealing with kill or capture missions on the west bank, the Defense Ministry decided to create a set of units (one for the IDF and one for the Police) that is collectively called Mista’aravim, or “pretend to be arabs”. The IDF unit, Duvdevan, is a highly trained SOF unit that specialized in being Arabs. They go into deep cover, the work on the west bank and can perform capture operations, intelligence gathering and a myriad of other tasks. Can a regular unit do it? Probably. Can they do it perfectly, the way Duvdevan does it? Hell no! Another example is Shaldag. These guys belong to the Israeli Air Force and are a cross between a Combat Controller and a deep reconnaissance unit. The go behind enemy lines and provide among other things precision target recon and laser tagging for the Air Force. They specialize in this, they train to do this over and over again. Can another recon unit do it? Yes they could potentially do it if needed. Can they provide the precision work Shaldag does? No.
Having small, very specialized units has provided the IDF with advantage on several fronts, including the digital warfare realm. Units within the military intelligence department that perform covert, offensive digital direct action ops, or the field intelligence unit where women serve as combat soldiers with men, and provide some of the most reliable intel directly from the field. Or more recently, specialized sniper units that can provide precision fire support to the different SOF units when needed.
Another example of a unit that was created with a specific purpose was Sayeret Egoz. Egoz was created as a response to the guerrilla warfare waged by Hizbollah in southern Lebanon in the late 80s and early 90s. Egoz specializes in this and learned to be guerrillas. To fight the way they fight. To be more Hisbollah than Hizbollah. In doing so they prevented countless attacks to Israel northern border and its towns.
In the picture above, can you spot the Egoz operator? Can you see the second one?
So, Israel has to adapt to an ever changing enemy. It is more effective to do so by creating very specialized units that can tackle the problem head on. Their counter terrorism school is one of the best in the world, with most of this units training heavily there and with the US and other ally militaries training with them.
I hope you have a better understanding on why the IDF has so many different SOF units.