Even though text-based terminals still see specialty use cases, modern general-purpose computers generally run graphical software and have a graphical user interface (GUI). This includes everything from low-end cell phones and some computer peripherals like printers, to fairly high-end servers.
I'd like for computers to be roughly on par technically with what we have today, but with user interfaces that are predominantly text-based. It's okay if these computers work with text blocks and things like that (for example, like how the IBM 5250 series of terminals worked), but except for graphically oriented work such as image editing, there should be minimal graphics.
Given that in our world, personal computers started becoming graphical pretty much as soon as they were powerful enough to run a graphical user interface at acceptable speeds, and some even earlier, how can I reasonably explain that GUIs never became mainstream?
Note that these computers need not be expert-only systems; I just want their interfaces to be predominantly text-based rather than predominantly graphical as is the case today in our world.
Also, to clarify, since there seems to be widespread confusion about this: Lack of a graphical user interface does not imply a lack of graphical capability. Take the original IBM PC model 5150 as an example; with the exception of those equipped only with a MDA graphics card, the software running on those often used text-based data entry with graphical visualization modes (what we in modern terms might call more or less accurate "print preview"). For example, something similar to the early versions of Microsoft Word for DOS or how early versions of Lotus 1-2-3 used different graphics cards and monitors to display data and graphs. Instead of thinking "no graphics at all", think "graphics only as add-ons to text, rather than as a primary user interaction element".
And since lots of answers imply that the only alternatives are pure command-line based interfaces and GUIs, let me remind you of tools like Norton Commander. I used Norton Commander back in the late 1980s and early 1990s, and still use look-alikes such as Midnight Commander to this day, and can guarantee that those can provide a perfectly useful environment for file management and launching applications that do not in any way depend on more than a text console. There is even a general term for these; Text-based User Interface, or TUI.