className is a small inconvenience when porting over an existing app to react (e.g. pasting in existing html), as is the requirement for style parameters to be

className is a small inconvenience when porting over an existing app to react (e.g. pasting in existing html), as is the requirement for style parameters to be objects. className is a quick find replace, but style is a more lengthy transpose process. These are small frictions, but in the same way that every ounce/gram counts to a hiker, minimizing process frictions makes a big difference in productivity during times you already have a high cognitive load.