To be fair, industry standard practices make it harder than it should be. We're making a very simple Vuejs app in our group (first one we've done in our group although we use Vuejs in other groups in our company). Our first stab out of the gate netted us nearly 500k of JS (production build, minified, etc) -- for something that basically takes a bunch of JSON and renders pretty tables.
Now, admittedly we've obviously done something horribly wrong, and the people on our team are senior enough programmers to accept that. However, if you're right out of a boot camp, or don't have a lot of confidence, then it might be something you overlook. If you've got a manager breathing down your neck saying, "It looks fine to me! Why are you wasting time trying to shave a few KB?", it can be hard to say, "Wait! This could potentially cost us customers". Having that conversation of "If we make the customer wait an extra second, they may walk away", is tough in the best of cases.
Ideally it would be very difficult to make as bad a mistake as we've made, but it really isn't. I suppose it gives us justification for larger salaries for experience :-)