Unless you assume the market for smartphone hardware with physical switches is the same as the one for sustainable smartphones, I don’t think they’re going to gain much from adding the switches. The only phones with switches that I know are the PinePhones and the librem phone that has a very questionable customer service. [1]. Adding them to the phone design will mean expensive constraints, making the overall cost even more in which case you’re either shedding money to increase market share or you’re narrowing your target market to the librem-phone size. At that point, what’s the meaning of this exercise?

[1] https://consumerrights.wiki/Purism