So, a little while ago climate change deniers used the fact of fluctuations in temperature throughout the year as a basis for a false claim that climate scientists were hiding the ‘real’ data in the less jumbly plots you suggest the use of. (And any sensible person would see the benefits of).

Whoever produced this is likely aware of those cynical and false claims, and decided they don’t want any risk the point they are making, being similarly undermined.