The short summary is: It's a suite of stuff that someone actually thought about making work together well, instead of a random assortment of pieces that, with tons of work, might be able to be cobbled together into a working system.

All the answers about the technical details or better/worseness mostly miss the point entirely - the public stuff doesn't work as well because it's 1000 providers who produce 1000 pieces that trade integration flexibility for product coherence. On purpose mind you, because it's hard to survive in business (or attract open source users if that's your thing) otherwise.

If you are trying to do something like make "code review" and "code search" work together well, it's a lot easier to build a coherent, easy to use system that feels good to a user if you are trying to make two things total work together, and the product management directly talks to each other.

Most open source doesn't have product management to begin with, and the corporate stuff often does but that's just one provider.

They also have a matrix of, generously, 10-20 tools with meaningful marketshare they might need to try to work with.

So if you are a code search provider are trying to make a code search tool integrate well with any of the top 20 code review tools, well, good luck.

Sometimes people come along and do a good enough job abstracting a problem that you can make this work (LSP is a good example), but it's pretty rare.

Now try it with "discover, search, edit, build, test, release, deploy, debug", etc. Once you are talking about 10x10x10x10x10x10x10x10 combinations of possible tools, with nobody who gets to decide which combinations are the well lit path, ...

Also, when you work somewhere like Google or Amazon, it's not just that someone made those specific things work really well together, but often, they have both data and insight into where you get stuck overall in the dev process and why (so they can fix it).

At a place like Google, I can actually tell you all the paths that people take when trying to achieve a journey. So that means I know all the loops (counts, times, etc) through development tools that start with something like "user opens their editor". Whether that's "open editor, make change, build, test, review, submit" or "open editor, make change, go to lunch", or "open editor, go look at docs, go back to editor, go back to docs, etc".

So i have real answers to something like "how often do people start in their IDE, discover they can't figure out how to do X, leave the IDE to go find the answer, not find it, give up, and go to lunch".
I can tell you what the top X where that happens is, and how much time is or is not wasted through this path, etc.

Just as an example. I can then use all of this to improve the tooling so users can get more done.

You will not find this in most public tooling, and to the degree telemetry exists that you could generate for your own use, nobody thinks about how all that telemetry works together.

Now, mind you, all the above is meant as an explanation - i'm trying to explain why the public attempts don't end up as "good". But myself, good/bad is all about what you value.

Most tradeoffs here were deliberate.

But they are tradeoffs.

Some people value the flexibility more than coherence.
or whatever.
I'm not gonna judge them, but I can explain why you can't have it all :)