Just a bit of info here. My engineer is quite the purist and the line he likes to use on me quite often is always "Anything in the signal path affects the tone. The purest path is always the simplest path". His feeling is that if the Di is designed right in the first place, any FOH engineer will be able to deal with the output level of the DI. Sure, you can ask a sound guy "Is my DI level ok?. Do you need more, or less?", but if you never bring it up and just present him with a usable DI level in the first place, the issue should never really come up.
And yes, while we are talking about just a few bucks in components, keep in mind I'm not just buying a couple buck worth of parts, I'm buying everything in multiples of 100, sometimes more if it's a special order part. A few bucks here, a few bucks there, really starts adding up when you are talking about a product with hundreds of components. We are trying to get the price on this amp as low as we can, given the design and every little bit helps.
I am genuinely interested to see if this is a feature guys are actually using, not simply a feature that players would like to have. The couple times I was asked about my DI level and I told the sound person that I didn't have any way to control it, he was like "No problem". So, in my experience, it's never been a feature that seems overly useful, as I've never owned an amp that didn't have a usable DI level.
The problem being that sometimes you get a FOH engineer, sometimes you just get a guy at the board.
The last nonsensical encounter I had with DI level I was using my Yamaha PB1 preamp into a Crown Drivecore amp. The dude at the board came by and plugged into my DI, saw where the level was set (around 8 o'clock) and said he likes to start off with it set at twelve.

I've only gigged with this pre for around ten years. I told him the output was pretty hot so try it where I have it, he insisted, I set it at 12 o'clock. He went back to the board, punched me in and asked me to play. Damn near knocked him out of his seat.
"You want to back that off a bit?".
"Sure".

I told ya so. If it were me and someone told me about a hot DI, I can't imagine why I wouldn't pad the input and bring the channel up slowly.
So DI level IMO is in theory unnecessary but real world you sometimes deal with the dude at the board. Be a bud and save them from themselves.