It's not about "heavy math." On a small-screened device like a phone, information density is more important, not less. This change dramatically reduces the density, so you have to do much more scrolling to see the same amount of information.

Add it to the list: if you are using a phone you are probably not... shopping, changing settings, signing up, using all the features, comparing products, reading longform, watching a movie, trying to do your job...