Why is Volume measured in shares and not in value?

[Chris_42]

If the volume of a share traded in a period is high and the price is high, it is certainly of interest. 

If the volume of a share traded in a period is high but the price is low, then why is it of interest?  We want to see where the real action is happening.

Why do we see charts where the number of shares traded is lower, but the actual value is higher because the price increased?

[MikeBamber]

Volume is the amount of trades. If there's 100  buys and 100 sells you have a volume of 200 but no price change (simplistic I know). 

My point is that volume and price aren't really related, it's more of a marker of activity.

[Bopperz]

If you use a smaller timeframe, you can approximate this yourself with volume*close. Then resample to the timeframe you are interested in.