“Newer” is not necessarily the same as “better” (incidentally, not just for programming languages).
Your misconception is that languages are old.The most widely used languages are certainly not, even if they are already at age. This is the same as someone from 40 called old while that person can still be fit and active and tremendously productive. (Well, if you are 20 then 40 is old. But for someone from 60…)
So you have to see it in the right perspective.All these old languages are regularly updated and equipped with new gadgets and techniques. For example, the ANSI C standard in version 11 has added support for creating multithreaded applications. And if you consider that C was born in 1972 then that is best at a reasonable age. But the language is so productive because of its simplicity so that it still dominates the software market. Certainly at the level of operating systems and “embedded systems” like the many Internet-Of-Things devices.
Old languages can ultimately be “retired” if their productivity decreases.They still remain in use because there is still a whole history behind it and there are still systems that work in these languages but their use decreases. But most of these languages will still get updates in order to continue to function in the present.
Think of COBOL and Pascal.Both languages were once very dominant in certain market segments. COBOL mainly for large companies on mainframes and Pascal as “Turbo Pascal” and later “Borland Delphi” on MS-DOS and Windows. Both languages are still maintained and you can still get compilers for these languages. Only, many developers choose other languages that make these languages lose their productivity. There are fewer experts.
But sometimes languages evolve as well.The old BASIC was a nice programming language for beginners and worked with line numbers where every statement of a line number was provided. Could you make very nice spaghetti code with it! But this language is not really more in use, even though there are some who are still trying to keep it alive. But BASIC evolved in Quick Basic and nowadays Visual Basic. The line numbers are gone, like some other outdated stuff but BASIC actually lives still…
And those new languages you mention?Those are not new! These have evolved from old languages with possibly a cross-fertilisation between two or more languages.
But old languages also have a huge history of applications that need to be maintained and updated.And that doesn’t just turn you into a new language. For instance, there are still companies that need COBOL programmers because their software is designed and needs to be updated regularly.
In addition to the other answers:
Many companies use software built years ago.There is a need for some maintenance on a regular basis, but often that is not enough reason to convert the whole source to a new language or even a whole new stack.
Complete rebuild is often a more years trajectory for several FTE.
Some companies then opt for gradual conversion because the store must remain open.
In the meantime, you still need people who know the old programming languages.
The skill in using a programming language is important.
Initially, the use of a new programming language produces a production version:
One of the features of many programmers is always wanting to learn.
And what could be nicer if in a new way use your brains through a programming language that is very different.
Can’t do this better, can’t this be any different?
But there must also be bread on the shelf.And where the new programming languages greatly stimulate programmers in thinking they are often not so productive in these programming languages. A programming language that is new also often has bugs that have never thought about anyone.
In order to put a working product into software, it is rarely desirable to use the latest technology, unless this technology offers a unique solution, or the solution may contain errors.
This is actually nothing else if (quick) add value and guarantee quality, and that is simpler with a well-known product in which someone already has experience.
A new programming language should add something unique to quickly conquer a strong market share.If this is not the case, a number of years of development will be established to get the language stable and to allow people to experience it. Then the programming languages become “old” by itself.
Furthermore, it is good to realise that many developments are not so new at all.In the years 60 and 70 of the last century, many of the things we now know have already been appointed, but it was not technically or economically possible to implement them on the scale in which it now happens.
The interesting question then is much more: what development has been in the past two decades where technology and money are still hampering.Because that is where the answer is for a new programming language.