What whitepoint should I use for calibrated monitors for print and web?

There is no "normal" viewing condition.

D-50 (5000°K) is an agreed-upon industry "standard."

The answer to your question is YES if you wish to eliminate sources of infinite frustration.

By the way, your clothing is important too since there are reflections. That's why all of us who work in colour seriously wear black.

Alternative practical solution: What we do to avoid keeping a step ladder and extra supply of bulbs around with different colour temperatures is to keep a specialized light-shielded "viewing" booth with the D-50 illumination inside. Not only the colour temperature is correct; but, just as important is the light intensity within the booth for optimal colour judgement.

In use, you'd switch off the D-65 overhead lighting and change the monitor settings to match.

A lighting booth is an additional expense but well worth it for colour management. Place it beside your monitor shielded from spill light to isolate it.

A display with a white point of D65 means that if you send it R=G=B=1 then the white has a CCT of 6500K (not blackbody but correlated). This does not mean that all white should always be D65; it can show all other 50 shades of white too, of course. So if everybody calibrates their white point the same then we'll all see the same white and ideally all other colors too. The only special thing about white D65 is that it is the brightest color that the display can render, because of R=G=B=1.

When the display is calibrated to D50 then R=G=B=1 gives a CCT of 5000K. If you have expectations what a print of R=G=B=1 (= blank paper) should look like under a standard (!) lamp of 5000K, then the D50 display will give you the most accurate preview.

Wit color management you can calibrate any display to match any other output device, like prints and photographs - under a given illumination ! This should save you the wasted proof prints, which is a major benefit of (digital) desktop publishing.

D50 may also be the preferred choice for viewing black-and-white movies on a color display, I learned that from Joe Kane. Or the movie could already be tuned to D50 (i.e. not R=G=B) in a color transmission, and then you should set the display to D65 in order to see D50 !

Various standardize color encodings and standard viewing environments have adopted different white points. As a previous answer points out, a display can be calibrated to any of these white points. This is done by modifying the chromaticity of the light emitted from the display when the code values R=G=B are sent you the display.

The television industry, computer graphics and others have adopted the standard of using the chromaticity coordinates for D65 as the display calibration white point, as well as, the chromaticity of the viewing environment or surround.

The professional printing industry has adopted the chromaticity of D50 as their standard.

Your choice of color encoding white point, display white point, and the chromaticity of the viewing environment should be based on the standards associated with your application (e.g. if your photos are going to be printed in a magazine with offset lithography vs being displayed on a TV set)

You should refer to the appropriate standards for each application (e.g IEC 61966-2-1, ITU-R BT.709, ITU-R BT.2020, ISO 3664, etc)

It’s worth noting light sources denoted as D50 or D65 do not spectrally match those daylight Illuminants. The are usually fluorescent sources, hence very spikey in nature, but have a chromaticity close the that of the denoted daylight illuminant.

As noted in CIE 15, there are no artificial sources that match the CIE daylight illuminant’s spectral power distribution.