Ken Scharf wrote:

RF power limitations (power into antenna) for the UK amateur radio
licences are expressed in dBW 26 dBW equals 400 Watts
15 dBW equals 32 Watts etc .

Why not just say Watts or milliwatts and be done with it?
Why drag dB into it?

Maybe because dB gives you a better idea of the limited communications
benefit to be achieved by turning up the power?

It also simplifies factoring in antenna gain, feadline loss, etc...

Really this is same idea as using a sliderule - take the log of
everything and then gain/loss becomes simple addition subtraction.

One downside though is that when playing around with a signal generator
calibrated in dB, you can fail to appreciate the degree to which you
may be turning up the power to something under test, at least until you
get used to the numbers.