Everyday language isn't so clear, simple, clean, lovely, concise and understandable - to a computer. However, to a human, readability counts for a lot, and the closer you get to a natural language, the easier it is to read. That's why we're not all using assembly language.
If you have a completely natural language, there are a lot of things that need to be handled - the sentence needs to be parsed, each word must be understood - and there is plenty of room for ambiguity. That's generally not a good thing for a programming language, because then we're venturing into psychic programming - the computer has to figure out what you were thinking, which is not at all easy to get.
However, if you can make something sufficiently close to natural language - and yes, Inform 7 is probably the best example - so sentences look natural, but still have some structure you need to follow - then the code is almost instantly readable, even to people that don't know the language. There's usually also less specialized syntax to remember - because you're really just talking (a slightly modified form of) English - but if you have to do something out of the ordinary, then you might have to jump through some hoops to do that.
In practice, most languages don't bother with this, because that makes it easier for them to allow you to be precise. However, some will still hover closer to the "natural language". This can be a good thing: if you have to translate some pseudocode algorithm to a language, you don't need to manipulate it as much to make it work, reducing the risk that you make an error in the translation.
As an example, let's compare C and Pascal. This Pascal code:
for i := 1 to 10 do begin
j := j + 1;
end;
is equivalent to this C code:
for (i = 1; i <= 10; i++) {
j = j + 1;
}
If you had no prior knowledge of either syntax, the Pascal version is generally going to be simpler to read, if only because it's not as complex as a C for.
Let's also consider operators. Pascal and C both share +, - and *. They also both have /, but with different semantics: In C, / does an integer division if both operands are integers; in Pascal, it always does a "real" division and uses div for integer division. That means that you have to take the types into account when figuring out what actually happens in that line of code.
C also has a bunch of other operators: &&, ||, &, |, ^, <<, >> - in Pascal, those operators are instead named and, or, and, or, xor, shl, shr. Instead of relying on some semi-arbitrary sequence of characters, it's spelled out more. It's instantly obvious that xor is - well, XOR - unlike the C version, where there's no obvious correlation between ^ and XOR.
Of course, this is to some degree a matter of opinion: I much prefer a Pascal-like syntax to a C-like syntax, because I think it's more readable, but that doesn't mean everyone else does: A more natural language is usually going to be more verbose, and some people simply dislike that extra level of verbosity.
Basically, it's a matter of choosing what makes the most sense for the problem domain: if the problem domain is very limited (like with Inform), then a natural language makes perfect sense. If it's a very generic domain (like with C), then you either need far more advanced processing than we are currently capable of, or a lot of verbosity to fill in the details - and in that case, you have to choose a balance depending on what sort of users will be using the languages (for regular people, you need more naturalness, for people who know programming, they're usually comfortable enough with less natural languages and will prefer something closer to that end).