It's about human psychology or human nature. DASH is supposed to be digital cash... being a good unit of account and user-friendly are important factors for this lofty goal.
Humans don't deal well with fractions or a bunch of leading 0's after a decimal (or comma)...
Imagine a cashier saying "that'd be zero point zero zero three six DASH ma'am" instead of maybe 3.6 DASH
This isn't an argument for changing the accounting unit, it's an argument for defining MANY accounting units. Most wallets are configurable according to how you want to denominate your holdings - it's a dynamic thing. For example in the mainstream economy, coffees are paid for in cents/pennies and pounds. Cars are bought with thousands, property is measured in "k" and national statistics are done in "B" (billions).
If you change what a "Dash" is it would be like changing the definition of a "dozen" from meaning 12 to 1.2. It's arbitrary. What do you do then when the marketcap goes through another revaluation and you end up using decimals again ? Change it again and keep moving the decimal to suit the purchasing power ? What reference market do you then use for your "optimal convenience" measure ? The price of a coffee or the price of a house ?
The fact is, day to day purchases will be made with stable coins anyway while fixed-supply assets are used for store of value. That's just how things work, so Dash is more likely to get used as collateral to back a stablecoin which you then spend in a market that has standardised price denominations, then spent directly IMO. It's a futile exercise, even if it's only "psychology".
The analogy of DASH and the word dozen doesn't really work. Dozen is just a word that means a set of 12. DASH is a crypto and has the goal to be programmable money.
Bitcoin used to have that goal too but has settled to be just a store of value.
That is only one property of money, money also needs to be a medium of exchange as well as a unit of account. Last I checked DASH still has these goals.
If DASH had already obtained mainstream adoption then I'd agree with you, no need to necessarily redefine the already accepted and known circulating supply and people would be used to displaying it in a way to avoid decimals. But most of the world still doesn't even know what Bitcoin is, never mind DASH. And if someone new to crypto were to invest in either DASH or EOS, knowing not much else, they'd likely choose EOS just because it's cheaper and they could have more.
But here's something curious... how many EOS are there? Coinmarketcap says it has a circulating supply of 936 million... however it only has 4 decimal places.
So if you take the smallest unit of each crypto, there are 970,000,000,000,000 pieces of DASH, that is 970 trillion duffs and there are only 9,360,000,000,000 pieces of EOS, that is 9.36 trillion pieces of EOS. Do you think if EOS had lowered it's circulating supply by a factor of 10,000 from the start, that is it had 8 decimal places instead of 4 and a circulating supply of about 94 thousand that it would have the same marketcap as it does now? Currently each coin is priced at about $2.71. Shift the decimal place 4 places and you'd need a per coin price to be over $27 thousand to maintain its current marketcap. There's no way I believe this would be the case. EOS would be lucky to be priced at $1000 and no where near to being a top crypto according to coinmarketcap.
So, it might be hard to fully understand but I don't think a re-denomination should be so quickly dismissed offhandedly without some serious study.
Too bad though, not sure I see much support for even that.