[KeplerBoy]

I did some reading and it seems you are right.

No Idea why phones come with a SAR rating then and why there are safe limits defined, when no one found unsafe limits.

[londons_explore]

Tiny amounts of cell heating/cooling have been found to change the cell differentiation mechanism. That's the reason ultrasound energies are limited during pregnancy and it's recommended not to do too many ultrasounds.

I don't see why microwave heating wouldn't cause the same effect.

[Mo3]

Because you tend to hold phones right to your brain.

[asdaq1312512]

Personally, I perceived it as a matter of good engineering: your phone shouldn't spend its energy to heat your ear.

[salynchnew]

Interesting! There might be other unintended issues from transmitting heat, I suppose?

Even from transmitting heat to the phone's components itself or other items that are nearby, e.g. laptops: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5219578/.

[atoav]

Afaik the transmission energy of a cell phone is limited to a maximum of 1 or 2 Watts (depending on which frequency it operates on). This power is a maximum that will only be used if the reception is bad.

In the wavie scene (people who are paranoid about radio waves controlling them) shielding those devices is a typical approach — this is also where the meme of the tinfoil hat comes from. Ironically that shielding makes your cellphone operate with the maximum transmission power at all times.