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. The internet as a whole consumes more electricity than the entire United Kingdom. So, if you’re the sort of person who gets excited about recycling, then you should also consider shedding some of that dead weight from your website.
I am completely for small, lightweight websites! I used to have a mobile phone contract that only allowed 100 MB a month, just over 3 MB a day. To avoid using up the limit in the first few days, I had to use Opera Mini, for example, and disabled data-hungry settings in almost all apps, if possible.