What do you call streets with shops/stores? Would commercial streets suffice or is there a more idiomatic term for this?
A common word in BrE is a parade. That is, a shopping parade.
In terms of usage, the assumption is that the row of units are exclusively dedicated to retail (perhaps having been built as a group), and the frontage may be pedestrianised.
In terms of a street that is considered to include a centre of retailing but not exclusively dedicated to shop units, and much more likely to have a road through for motor vehicles, the most likely term generically would be the high street (even if the street is not itself called High Street).
If you're talking about an area that has multiple streets with a concentration of many shops, you'd normally call it the town centre.
"Market street" would be the term that I would hear amongst expatriates speaking English to describe such streets overseas - although that had the implication of merchants and vendors mixed among the stores, not the sterile streets of franchised stores.
I suspect it mostly depends whether you're using the word to describe where the character in a novel is walking, or technical writing to guide tourists to specific commercial districts, etc.
One definition of a mall is a street lined with shops, although we usually think of a mall as a shopping center.
In support of the word parade, a shopping street may include a Parade which, to me, evokes a section of a road/street where the shops adjoined each other, i.e. a street which included a parade of shops and normally (as I recall) only on one side of the street/road. Sometimes parades are set back from the main road and has an exclusive slip road for temporary parking of vehicles. This road then rejoins the same main road
Google supports this to an extent with: Shopping parades are purpose-built rows of shops, often with generous residential accommodation above. They were built in large numbers, and with increasing architectural elaboration, from the mid-nineteenth century.
Why not this word?
strip malls: a shopping mall consisting of stores and restaurants typically in one-story buildings located on a busy main road.
Or this in the contexts of small business vendors on a littler thoroughfare
street market / farmer's market: a small street with shops and restaurants
If the vendors are selling used wares:
any part of a city or town in which the primary land use is commercial activities (shops, offices, theaters, restaurants and so on), as opposed to a residential neighbourhood, an industrial zone, or other types of neighbourhoods
Wikipedia also suggests "commercial zone," in reference to the fact that such districts are often established by local zoning laws that control where such businesses can be located.