A pro will notice things about implementation that interfere with the content, while the layperson often can’t articulate it even if they sense it’s not quite right.
I've had plenty of friends and acquaintances observe that browsing the web on my computer is very zippy compared to doing it on theirs, and ask what I do. I hate to then have to explain to them that it's because of a fairly hard-won set of JavaScript-blocking rules and suchlike.
I especially hate it because the best alternative I can suggest to someone who doesn't understand tech well enough to manage such a thing is to just keep on trying to keep up with whatever fancy kit Web developers are working with these days. Which invariably means sending ever more money to Comcast. And regularly giving money to Best Buy to replace a computer that isn't really broken; it just can't keep up with the latest fashions among ad networks and reactjs developers.
Wait, how often are people peering over your shoulder to even notice? Have been a programmer for 30+ years and no one has ever made an observation either way about my screen responsiveness...
For those unaware, an empty house can go untouched for decades in NYC, but once it develops a broken window, it is ransacked and squatted within hours. Small failures invite large failures.
"Javascript bloat isn't too bad, just another 10KB" turns into (VERY quickly) slow + terrible code that is trash. Small amounts of apathy about code invites other developers to sink to lower (more sh*tty) standards until there is nothing good left.
I'm not saying we should all code in assembly and c and make sure our arrays are memory aligned and pointers efficiently used, etc. etc., but we should also not just stop caring about code quality for "productivity" sake.