Puzzler, this stuff isn't written in Basic anymore as it's all been done before and nowadays there are far easier languages to work with to do these types of programs.
When Basic was written, in the 70's, it was one of the best all purpose languages around. The fact that 30 years later that it's still in use by many of us proves how good a language it is. Microsoft thinks so to, otherwise it wouldn't still be putting it on its CDs. Think of all the other languages that have come and gone since Basic was written, Fortran being just one, even COBAL is being phased out of schools and colleges as the learning language of choice. Prolog's specialty was AI, it dropped out of sight for a while but was revived a year or so ago.
Melissa is right, at one time there were hundreds, maybe thousands of professional, commercial programs written in Basic and its variations, GWBasic, QBasic, Asic, QuickBasic, BasicA, Basic2, Basic2 Plus etc. etc. as well as the all the tools, libraries and utilities that are now commonly written for VB, C, C++, Delphi etc.
QBasic programs can be as complex as anyone cared, or can care, to write. It's got all the tools necessary to get to the underlying software and memory. A company I used to work for spent a fortune getting the programmers copies of the MS Development software but even then I sometimes found it easier to write code in QBasic. As MS moves away from DOS based OS's then the problems with writing programs where you draw on the resources of the OS will only get worse for Basic - you need only look at what some of the earlier mouse programs do to a PC running some of the later Windows OS's to understand that.
Personally, I'd hate to write some of the programs and routines you mentioned in your original post in QBasic, as I said, it's easier and faster in other languages. That's progress, otherwise we'd all still be using Assembler, or worse still Machine Code. As a program to learn programming techniques, it's great. I'ts free and there are millions of lines of code to examine. Besides that, I and many others, still like using it. You need only look around the net to see how many people are using it, what they are using it for, and from the emails I get to my site, are still interested in learning it.