VU meters seriously under-read peaks. Does that make them useless? Or can the VU meter really help you to improve your recordings and mixes?

NOTES
Regarding my question (   • Virtually Useless? Hear what VU meter...  ) on where did the equivalence between 0 VU and -18 dBFS come from, a kind commenter has pointed out that it's in EBU Technical Recommendation R68-2000 Alignment level in digital audio production equipment and in digital audio recorders. The recommendation doesn't mention the VU meter specifically, but we can probably infer this.

Regarding copyright in the song (   • Virtually Useless? Hear what VU meter...  , YouTube's Content ID system hasn't picked this up so the audio can remain available for now. This may change in future and I will be happy to comply with the copyright owner's wishes. You can find links to the song and artist in the credits below.

CLARIFICATION
At    • Virtually Useless? Hear what VU meter...   I mentioned the Revox B77 being aligned to 200 nWb/m = 0 VU. A tape recorder needs to be aligned to the type of tape being used, using a calibration tape for playback alignment, then the tape to be recorded for record alignment. Tape recorders were normally sold with a recommended tape brand and type so that they could be delivered factory aligned. The recommended tape may have been different in Europe and North America. A competent technician could align the machine to any brand and type. In this instance the B77 was aligned for Ampex 406 tape. Some commenters have mentioned nanowebers per square metre. This is incorrect. The measurement is nanowebers per metre. DM

CREDITS
King Alfred infiltrates the Danish camp - Joseph Martin Kronheim
The Fall of Princes - John Lydgate
Milton Dictating to His Daughter - Henry Fuseli
Haiku - Matsuo Basho
VU Meters - Crookwood
Revox B77 - Touhotus CC BY 2.0 (both pics)
Max Verstappen - Morio CC BY-SA 4.0
Sergio Perez - XaviYuahanda CC BY-SA 4.0
Vocal - Chilli Gold
Guitar - Mick Hutchings
Drums - Joe Clancy
Mix - 'I Wrote A Song' by Mae Muller https://www.maemuller.com/    / @maemuller   https://maemuller.lnk.to/IWroteASongID https://en.wikipedia.org/wiki/Mae_Muller