Intriguing question. Looking into it I found some interesting facts. Wikipedia says:
Old English had a single third-person pronoun hit and was used for both people and objects (inanimate or abstract). In the 12th century, it started to separate and appear without an h. The hit form continued well into the 16th century In Modern English but had disappeared before the 17th in formal written English. Genitive its appeared in the later 16th century and had taken over by the middle of the 17th, by which time it had its modern form.
The following sentence is interesting
"Hit" remains in some dialects in stressed positions only; some dialects also use "it", not "its", as a possessive.
So that implies that there WERE cases of stressed HIT in the past.
AHD confirms this saying
In some American vernacular dialects, speakers may pronounce it as hit in stressed positions, especially at the beginning of a sentence, as in
This pronunciation is called a relic dialect feature because it represents the retention of an older English form. In fact, hit is the original form of the third person singular neuter pronoun and thus can be traced to the beginnings of the Old English period (c. 449-1100). Early in the history of English, speakers began to drop the h from hit, particularly in unaccented positions, as in
Gradually, h also came to be lost in accented positions, although hit persisted in socially prestigious speech well into the Elizabethan period. Some relatively isolated dialects in Great Britain and the United States have retained h, since linguistic innovations such as the dropping of h are often slow to reach isolated areas. But even in such places, h tends to be retained only in accented words. Thus, we might hear
side by side with
- I took it back to the store.
Nowadays, hit is fading even in the most isolated dialect communities and occurs primarily among older speakers. This loss of h reflects a longstanding tendency among speakers of English to omit h's in unaccented words, particularly pronouns, such as 'er and 'im for her and him, as in
- I told 'er to meet me outside.
This kind of h-loss is widespread in casual speech today, even though it is not reflected in spelling.
Now I know that this is very linked with pronunciation, but English does stress words, including pronouns, through intonation or change of pitch:
Stressing personal pronouns often emphasizes that one person or persons is being contrasted with another. A change in pitch often accompanies the pronoun that has been brought into focus through stress. When this happens, the overall rhythm and intonation of the sentence changes, sometimes significantly. (source)
So, the fact that modern it lost the h, might indicate that it simply ceased being used in stressed positions in the process. Why that is would definitely be interesting to know... Could it be related to our inherent understanding of the superiority of persons over inanimate objects?
Addition: The way demonstratives behave with phrasal verbs (sorry for those who do not agree with this term), may shed some light:
Q: If I start a plant indoors and then move it outside, I can say either “I will harden off the plant” or “I will harden the plant off.” But if I use a pronoun, I can only say “I will harden it off,” not “I will harden off it.” What’s going on here?
A: When this kind of phrasal verb has an object, and the object is a noun, the noun can go either in the middle of the phrase (“harden the seedlings off”) or at the end (“harden off the seedlings”).
But if the object is a personal pronoun, it has to go in the middle (“harden them off”), not at the end (“harden off them”).
(We should add that while personal pronouns can’t go at the end, demonstrative pronouns can: “this,” “that,” “these,” “those.” Nobody blinks when we say things like “Did you harden off those?” or “Please hand out these.”) (grammarphobia)
Conclusion? Yes, demonstrative pronouns are obviously stronger candidates for stressed uses than any personal pronoun, let alone it.