In theory modern power is more stable at the source, but we have FAR more things downstream between source and you that can effect power stability. (here at work each of my critical servers are behind a device called a power conditioner. it is essentially a $1000 set of capacitors and circuits)
ALL modern appliances from phones, to blenders, to cars have capacitors in the circuits for power management.
Noise suppression, power stability, circuit protection, etc. MANY uses.
You do not seem to me to be argumentative, seems to me that you are being inquisitive.