Battries have finite lifetime. Assume you have a battery that is rated 500 cycles lifetime. If you do 20%~80%~20%~80%~20%~80%~20%~80%~20%~80%.... Then you got about 1000 cycle lifetime, Still way lower than infinite. --- Post updated --- This is about internal resistance, most li-ion battery is rated 3.0V~4.2V voltage, the perceived voltage is higher than actual when charging, when the perceived voltage reached 4.2V the charging speed goes down even though the actual voltage is still lower than 4.2V, otherwise you risk overcharging the battery. Similarly, EVs will lose horsepower when the battery is lower than 20%, which don't happen in ICEVs. --- Post updated --- No, it's not about political "ism"s, its about cost effectiveness, when they use EVs batteries as a ballast to "balance" the power plants. They'll immediatly notice that their plants are working more efficiently, but it'll take years to be noticed, the cost of replacing dead batteries(battery has finite cycle lifetime) is way, way higher than the cost saved by running plants at a slightly higher efficiency. Sadly those polititians don't even know about delayed gratification. Also, when doing this, EV owners have to plan their livings in advance, so this scheme is acturally restricting user freedom.