Why are Roman numerals still used?

It's mainly just inertia. Roman numerals were already being used, so in many contexts they're still used. Much like that double-l in still.

There will be a plethora of subsidiary reasons. One that comes to mind is that Roman numerals may lend a touch of 'gravitas' - making your clock or film, for example, look a bit more classy because of the historical associations.

I've often heard that Roman numerals on tv/movie copyright dates are partly intended to be obscure so you don't dismiss something as 'too old to bother watching'. But I think that's an urban myth, since you don't normally see the copyright notice until after you've watched the thing.

They have many other uses. For example, in music theory, they denote the chords based on the steps of diatonic scales. For example, I-IV-V represents the standard "three chord" rock or blues chord progression. In upper case they represent major chords, in lower case minor: I-vi-IV-V⁷-I. Note that the V7 combines two number systems, the first for the chord position, the second for the alteration (in this case the dominant 7).

As Wikipedia notes:

Classical numbering is often used to suggest importance or timelessness, or in other cases where an alternate numbering system is useful for clarity.

Hence monarchs and popes use Roman numerals after their names: Elizabeth II, Pope John XXIII, Louis XIV, etc. Even ordinary people use them when they hand their names down to their children: August Busch IV (former chairman of Anheuser-Busch, for example).

Outline form often uses Roman numerals in conjunction with letters and Arabic numbering to make clear distinction between levels of hierarchy. Open up Word or another word processor to see this in action.

The only acceptable reason to answer your question is, it's hard to stop using something which is widely used. it has grown to be something that is widely used by everyone in today's society:

• They are still used in almost all cases for the copyright date on films, television programs, and videos
• They are also used to show the hours on some analogue clocks and watches.
• They are used for the preliminary pages of book before the main page numbering gets under way.
• Sporting events are often numbered using Roman numerals.
• Monarchs are usually numbered in Roman
• This form is also sometimes seen in naming eldest sons in American families where successive generations bear the same first name.
• They are found in numbering paragraphs in complex documents to clarify which are main sections.
• Roman numerals can be seen on public buildings, monuments and gravestones, sometimes when the inscription is in Latin but often just to give the date a certain gravity.
• They are an additive (and subtractive) system in which letters are used to denote certain "base" numbers, and arbitrary numbers are then denoted using combinations of symbols.
• Roman numerals use letters to represent values.

Roman numeral-history and use.

They are used at the end of TV shows supposedly because the copyright laws require a date but the makers don't want the show to look old - so they put

(C) MCMXCVIII

rather than 1998