If an adversary has physical access to a computer, they can get basically anything. In unencrypted scenarios they can pull out drives and mount them in their own run time (OS). If the device is also running then coldboot attacks can allow the encryption to be attacked.
Finally, there is the eventual cracking of many encryption algorithms via cryptanalysis and moores law.
Cold Boot is hard to implement, and can be mitigated by putting the 16kb of key memory on the L2/L3 cache or some other piece of memory that instantly clears on power off.
With FDE and memory encryption, how else can you get pass this?
Thing is, you would know if someone broke into your house with a rock through the window. Breaking into your computer, or breaking the encryption of your data on some server, can be done without nobody noticing for years.
Securing your data is a completely different problem, and a much more difficult one, than securing your house.