Thankfully most languages didn't make this mistake but some did: CMake, YAML, Bash, TCL. All notoriously awful.
"Sincerely," "ls" "-lah" "foo" "bar."
Alternatively it could let you type without quotes and then automatically quote it for you (e.g. you press shift-enter and it auto-quotes it).
It's fine for interactive use because you can debug errors when they happen. The issue is with scripts.
The problem with “works most of the time” is that it stops working when you’re not around. So it might be fine for a one-off shell command, but you never know what the next guy will pass into it.
Generally a good idea if you care about bugs at all.
Could you elucidate?
The biggest problem I see with people dealing with Tcl is that they carry their understanding that {} delineates scope (or something else lexically). Of course, this is wildly untrue in Tcl as {} is simply a "quote" operator.
This stuffs people up horribly until they unlearn the idea that {} has semantic meaning.
puts Hello!
puts "Hello!"
puts {Hello!}
# or even
{puts} {Hello!}
# x is not actually a list, but may appear that way if a and b are nice
set x "$a $b"
# Proper way:
set x [list $a $b]
As well as Perl and PHP, though both have since recanted (Perl started 20 years ago with strict mode, which IIRC forbids barewords in most contexts; and PHP deprecated barewords in 7.2 and removed them in 8).