A character might need to make a roll at a bookkeeping profession to see if records have been altered. . .or to alter records to cover up something. They might need to roll as a candlemaker to make a particularly high quality candle (like if they were helping a mage make a candle-based magic item like candle of invocation). They might need to roll as a farmer or green grocer if they were trying to help a farmer or grocer turn their business around and help them out by doing a very good job on the farm or at the store.
Bookkeeping alterations are covered in INT (investigation) and helped by forgery kit proficiency per XGtE. A background related to bookkeeping might accomplish the same thing based on using backgrounds for proficiency.
There are rules for creating magic items in XGtE as well, and they do not include rolling to make high quality items. It's a given.
I'm just trying to wrap my mind around a very different mindset of D&D.
So, for example, if it's someone's background, letting them add their proficiency bonus to related tasks/knowledge from their background (that aren't already covered by other skills/proficiencies)?
Maybe letting players learn a profession (equivalent ability to being able to doing the checks with their background) with the same time/training rules for learning a language or a proficiency in a set of tools?
Like with my soldiering example, if it wasn't their background, but if during the campaign if someone spends 250 days in a regular army, let them gain essentially "proficiency" with soldiering and be able to use their proficiency bonus on appropriate checks?
The only thing the soldier background gives that isn't already available is the rank. A person can learn languages and tool proficiencies via downtime already, and a feat for skilled (or prodigy) adds the same skills if they are not already present. Recognizing military rank is something that takes very little time to learn.
A DM determines if the actions a character takes needs a check and what contributes to that check. IME, standard proficiencies plus situational background proficiency is pretty common. If a person wants to "add a background" then the skilled feat covers 3 skills instead of 2 while languages and tools can be learned. Any additional background feature "from a lifetime of..." becomes situation as a boon up to the DM.
Backgrounds are also examples. Make a custom background and use that to make your profession working with your DM.
In the real world, learning the profession of being a Soldier takes a few months, same for being a police officer. You can learn a lot in a few months of downtime.
D&D games I've played in have often had weeks or months of downtimes between adventures, especially between plot arcs.
Which explains why it's reasonable for someone with no training to make untrained checks if the DM warrants it getting back to PC's having seen military ranks and processions at some point as an assumption.
So, back to the lawyer example...
Which gets to another point -- what the profession actually does. INT (history) would cover precedent while CHA (persuasion) would argue the case. Make a lawyer background and use those as the proficiencies. A feature might be similar to the sage in knowing where to find the legal information.
4e had a Dungeoneering and Streetwise skill and I feel like both are somewhat missing... More so Streetwise than Dungeoneering. Streetwise allowed you to gather rumours in a city, get the lay of the land and navigate the city. It could easily have Commerce folded in and form some sort of Urban skill (opposed to Nature). Dungeoneering wasn't quite as well defined since it covered both natural caverns (which are now simply Nature), the Underdark and building exploration (architecture for exemple could be a Dungeoneering check).
Sailing would probably be best represented by proficiency in sail boats and other water vehicles. Folklore and Nobility could easily be folded into History, same with Military really, but I would give out advantage based on your background.
Some of those are examples of checks made without proficiency. Urchin enhances navigating the city while gathering rumors is a CHA check right on the list. I think most DM's just RP those out, however, ime.
OK, a few problems with this example: 22DC don't exist, they go in 5s. Incompetent Carl can't even attempt a 25 DC. However, a Level 17 Wizard with a Strength of 10 who happens to be trained in Athletics (an Outlander Wizard, say) can make that roll.
Minor correction. DC 22 does exist. Not all DC's go up by 5 such as spell DC's or opposed checks. The difficulty DC's step by 5's.
Mind you, that doesn't change the fact 5e checks work for me. All I need is to have my character perform actions. It works or it doesn't or the DM says roll (x proficiency applies). If I want to soldier or lawyer it's not hard to build something to concept. ;-)