Yes, I accept that you will hear “I promise (that) I will …”. This
may be for several reasons:
- (i) the speaker's native language isn't English;
- (ii) the syntax of the speaker's native language doesn't allow
I promise to + inf, it only allows promise that … (or some
other construction);
- (iii) the extent to which the speaker feels “will” is a simple
expression of futurity or a modal expression of
willingness
Will jako prostředek modality dispoziční
vyjadřuje různé odstíny volní dispozice k ději … ( emsa 8.44.71 )
- (iv) the extent (if any) to which the context is stylistically or
emotionally marked: in negative statements (like the three you
quoted) the speaker may feel the need to emphasise the unwillingness by saying
I promise I won't instead of I promise not to. In simple
(stylistically unmarked) declarative affirmative statements,
the speaker may feel the sense of willingness is already conveyed by
“promise” and doesn't need to be reinforced by using “will”.
Note also
the comments at the end here, suggesting that the version with “will” might
be stylistically marked:
- I promise to ring you later.
- I promise that I will ring you later.
They both mean the same thing. I would nearly always use “I promise to
ring you later” simply because it's quicker to say. I suppose there might be
a very slight difference in that “I promise to ring you later” just means
that the person will ring later, but “I promise that I will ring you
later” could suggest that they may have forgotten/not called before when they
said they would but this time they are promising they will call. However, they
do mean the same thing but in some contexts of the 2nd option, there may
be a hidden suggestion that they didn't call before.
The Ngram
doesn't, of course, tell us everything, but it does tell us something.
So there's often a potential problem when we're analysing a single sentence
out of context because we don't have any clear sense of what
stylistic marking there may be in context. In an exercise
featuring the out-of-context affirmative declarative statement “I promise
---- get to work on time every morning (in future)”, I would definitely
recommend “I promise to get to work …” though, as I said, “I promise
that I will get to work …” isn't incorrect.
Postscript: … out
of the mouths of babes and sucklings … [ … z úst kojenců a
nemluvňat]: here, a cute
little girl promises that she won't eat
animals! – it's a strong expression of her will. If we said
she promises not to eat animals, it would sound too weak.