Technology is supposed to be there to serve us, to make life easier. Automated things can most certainly make life easier, but they don't when whatever is being automated is for something which has multiple options which have no fixed or set logical outcome each time - i.e. user preference.
More indepth to cover some of the points raised here in the answers/comments, and in some of the duplicated questions.
Our choice of new tab or not changes based on scenario, from from one link to another, from one day to the next.
Our decision changes towards whether to new tab or not new tab, and the function (or the programmers of it) don't know which outcome each individual user wants to occur, so it cannot be automated.
I sometimes open linked questions in a new tab if (eg) I'm learning something complex and want to refer back to a previous answer (etc). And sometimes it wasn't the answer I wanted and so don't want to open a new tab with the linked answer.
This extends to many other scenarios with various different link types, where I change my desired outcome, and surely you (reading this) are the same?
In fact, I can sometimes want a different outcome for the same link on different days, depending on what I'm doing that day.
We have various "simple built in and default" options to open a link in new tab (which I sometimes do), however we do not have various "simple built in and default" options to not open in new tab.
Open in new tab by:
- Ctrl left click
- Middle mouse button (as standard or can be set)
- Right click choose "open in new tab"
Not open in a new tab by:
- Fiddle with my browser config
- Install an add-on
- User script
- Probably some other "in depth" options which potentially affect other
scripts or cause unforseen problems as it's not "built in/standard"
We can open a new tab currently with a few choices of built in options, however not opening new tabs we do not without scripts or addons etc. By implementing automated new tabs, we force users to have to use scripts and configs to stop them, whereas currently no-one has to do that and essentially everyone is catered for.
The website cannot please everyone, and so the least problematic outcome is catering for those with the least control - those who cannot stop a new tab easily.
Only some links
It does not matter what links this is for - external, internal, profiles, JSFiddle, etc. In fact, mixing which links do and don't automatically open in a new tab is the problem with the internet and websites.
Some sites open new tabs, some don't, and some even only open new tabs on some of their links.
This is like eating a bag of revels blindfolded.
We just do not know when a link will open a new tab, or when it will not = we have no control as over the internet as a whole it's entirely erratic.
Some people are voting and suggesting for only certain links to be opened in a new tab, eg JSFiddle, or user profiles. So user group A knows that links to "JSFiddle on Stack Exchange sites" open in a new tab. Well, jolly wonderfulness for them users. What about everyone else who doesn't?
What if user group A gets their wish, and user group B wants another "specific" type of link to open in a new tab? user group A then clicks that link and unexpectedly goes to a new tab.
Do we change it back because user group A didn't want that?
Do we change the JSFiddle links to not open in a new tab because user group B doesn't want that?
Who are we serving here? Who gets their own way? Why are we even fighting when the simple solution is that all links (ideally on all websites, but yeah) do the same thing! Then we know what will happen each and every time, and can plan and use our own personal methods and desired outcomes each and every time.
Internet a better place
If the entire internet "did not" open new tabs automatically, then we could flow through our usage of websites with ease, with predictability and using our own personal methods.
If we want to leave the page then simple click the link, if we want to keep the page and see the linked one as well, open in new tab - this is using technology to our advantage.
Automated new tabs sucks more than a half starved anteater finding a previously undiscovered ant colony.
Automated new tabs are just not logical captain.