I can answet that, qith question. Did you saw game made by Epic which is done fully in blueprint, except Tappy Chicken ?
While blueprints are awesome, nice, and it’s best thing since sliced bread(no arguments!), I don’t think most people even consider making serious game fully in them.
As an end point they are great (connect few nodes, like 4-6 and buf! you have new gameplay element, which just call to pre setup C++ interface) or as for prototyping, I can hardly imagine someone making fully big game with them.
Just because there is hammer around laying, doesn’t mean you should use it to kill flies.
The same IMO is going for other non C++ languages. With even less benefits. Blueprints are fairly easy to understand by virtually anyone. While written languages, are not. For me it doesn’t make any difference. But people who never wrote line of code, doesn’t care if it C++, C#, Go, Visual Basic. It’s the same arcane magic beyond understanding at first glance.
Aside from that. There is no real reason to implement anything else. Hardness of C++ (especially in wrapped version in UE4) is mainly based around prejudices, not any facts. Look, there are people around forums, who are artists, and yet know how to code in C++ ;).
They add features, that most people want(and what they need). As you can easily judge, people around don’t want scripting integration from Epic. More over most people seems to be clearly opposed to such thing.
Because it would take resources, which could be used to add new features, that are actually needed, or improving existing ones.