SARMs are commonly prescribed by doctors to men with hypogonadism (low testosterone).
They are basically a way of treating low testosterone without prescribing testosterone.
The main point of this is due to the fact that testosterone therapy is typically associated with all kinds of negative side effects (similar to anabolic steroids) that result from extended use.
One of the benefits of SARMs is that they are orally bioavailable. In other words, they can be ingested in pill form and find their way to cell receptors just fine in low doses. While there are new advancements that have led to orally available testosterone (actual testosterone pills), the common (and more effective) way it is administered is via injection.
The issue with injecting testosterone is that it can create wild fluctuations in both total testosterone and free testosterone. In the event that something goes wrong – these high levels remain in the system for a long period of time.
Testosterone patches are another common way of treating low-testosterone but they carry with them similar risks and, on top of that, there can be unintended dosing of people who rub up against the patch such as women and children.
SARMs generally create much lower fluctuations in androgens into the system. That, in and of itself, supposedly makes them less risky than testosterone when administered correctly.
Again, the whole point of SARMs is to avoid the negative side effects of testosterone administration.