Kevin Galligan wrote a metronome with HTML, CSS and JS, which has a total size of less than 1 KB. Because the existing ones were as large as 11 MB without more functionality. In the accompanying blog post he rants about the modern web (with data-based proofs) and explains how he achieved to make the metronome app as small as 1 KB.
The overweight web also has an environmental impact.
I have around 36 hours left until the current period of my mobile data plan expires. Each period takes 28 days and I have 2 GB of mobile data and endless calls and text messages available, for which I pay 7,99€. With the start of the next period I have 3 GB each 28 days.
In the current period I still have 1,8 GB left, so I only used about 10%.