People use what they have, I won’t blame them for it. (Although the notion that web apps—such as Facebook, GMail, Google Docs, or PDF.js—are less resource-intensive than “normal” desktop usage does not seem to hold much water to me, and those are usually included when a machine is said to be used “just for web browsing”. So if the experience ends up quite miserable I won’t be surprised.) But I’ve shopped for a laptop for a relative some months ago and am a bit testy about how manufacturers seem to be saving money on frickin’ RAM (or more realistically segmenting the market using it). Just... don’t fall for it if you have a choice.

if the RAM is upgradable then I'd say yes.. 8GB RAM stick costs ~25€ and anyone with a screwdriver can make the swap...

if it's not upgradable then it's up to the user to determine if it's worth it to replace the whole laptop, but if it has 4GB of RAM its other specs are probably gonna be outdated as well and you can buy very good refurbished laptops for under 300€ these days...

4 Gb is not enough for browsing, at least with Firefox on Linux with more than 10 tabs.