There's a difference between Hadith and History. Hadith is NOT History.
Though history isn't totally reliable, it's a lot more dependable than hadith.
History is the study or recounting of past events and activities involving one of the following methods or all:
1) A chronological record of the events of successive years. A periodical journal in which the records and reports are compiled.
2) Narration or story, which is an account or recital of an event or a series of events, either true or fictitious.
3) Version, that is, description or account from one point of view, especially as opposed to another.
For instance, how do historians know of the events that occurred in the Philippines before the time of the Spaniards? How do they know the names of the people who lived then and the things they did if there are almost no authentic written documents from that era?
Traditionally, historians have attempted to answer historical questions through the study of written documents, although historical research is not limited merely to these sources. The sources of historical knowledge can be separated into three categories:
(a) what is written,
(b) what is said,
(c) and what is physically preserved.
Historians must consult all three.
Good historians frequently emphasize the importance of written records, which universally date to the development of writing. This emphasis has led to the term 'prehistory' referring to a time before written sources were available on a particular event or personality etc. Since writing emerged at different times throughout the world, the distinction between prehistory and history often depends on the topic.
The scope of the human past has naturally led scholars to divide time into manageable pieces for study. There are a variety of ways in which the past can be divided, including chronologically, culturally, and topically.
Traditionally, the study of history was limited to written and spoken word. However, the rise of academic professionalism and the creation of new scientific fields in the 19th and 20th centuries brought a flood of new information. Archaeology and other social sciences were providing additional information.
Thus, history has more than one approach for authentication and verification.
As for Hadith, it has only one source which are narrations with only one 'verification' i.e. isnad, the unreliability of which has been detailed in the post "Ever thought of fallibility of Isnad?"
Moreover, history doesn't have a 'fragile ego' like Hadith. Even if certain historical reports are doubted, history does not take that as an infra dig. No data compiled by humankind can be one hundred percent reliable, no matter how carefully it's been acquired (which of course is NOT the case with Hadith). On this very basis, human historical narrations are never made a source of law.
The altered versions of Old & New Testaments and Hadith are human narrations. In connection with history, the only difference between the two are - Hadith narrations are written information of the narrators but without any proof of its reliability except the Isnad, which evidently has been constructed & re-constructed in most cases and cannot be relied upon at all. As for the altered Old & New Testaments, since these started being re-written hundreds of years before Hadith, there's no record of the culprits who began this practice. And obviously because the Jews and Christians brought the changes directly onto their Divine Scriptures, it was still more necessary to conceal the identity of those who did this.
It is the concept of tracking Isnad or the chain of narrators in Hadith that we often hear of as the 'Science of Hadith' or the 'Hadith Methodology.' Unfortunately, these bombastic terms that frequently impress the minds of many a naive faithfuls are just the facade with an ostentatiously lofty style but in reality quite hollow from within. The enormous scope for the Isnad to falter which is far greater than the possibility of its correctness is conveniently concealed in this so-called "Methodology" myth.
It's more than evident that the source of Hadith as history is thoroughly insufficient compared to the various other extensively researched and compiled historical data that involve more than just narrations or chain of narrators