Avadhi and Brajbhasha are no longer considered prestigious languages in North India, and their speakers are often thought of as गँवार (aided by the fact that most of their speakers today, live in villages)
This is quite ironical given that till the late 19th century, these were the most prominent languages for composing epic works in Hindi literature. Both Tulsidas’ Ramcharitmanas and Malik Muhammad Jayasi’s Padmavat were composed in Awadhi, while Surdas’ Sursagar and Mira Bai’s verse were composed in Braj Bhasha.
What we call Modern Standard Hindi, came into its own only in the 1860s and 1870s when a brilliant young scholar by the name Bharatendu Harishchandra translated classic Sanskrit/Bengali/English plays and works into the Khadi Boli dialect, along with many original compositions.
Despite a history of monumental poetic works, neither Brajbhasha nor Awadhi had any works in prose to speak of, and with rising literacy, Harishchandra felt an acute need for a language that could serve the literary needs of the time, while at the same time, possessed a continuity with traditional Hindu thought and mythology.
He finally chose Khadi Boli in the Devanāgari script, mainly because it had already been popularized in the form of Urdu, and had gathered enough prestige (and comprehensibility) by the time. True to its purpose, this new strain of Khadi Boli borrowed vocabulary and themes more heavily from Braj, Awadhi and (especially) Sanskrit, compared to Persian.
But even till the early 1900s, Hindi authors continued preferring Braj and Awadhi for composing verse, and kept Hindi mainly for the purpose of prose. Starting from mid 1910s though, Hindi started becoming widely acceptable for composing poetry as well (and took off, in a manner of speaking)
Its an object lesson in the fact that mellifluousness and sweetness of tongue is more a function of what you’re habitual of, rather than any objective standard. Khari Boli, which was once derided as “vulgar” is now the standard prestige dialect, while the once “cultured” and “urbane” Awadhi and Brajbhasha, are now considered “abhadra” and uncouth.
P.S: The term “Hindi” was often used for many Indian languages, Urdu included, but starting from the 1860s, it began to be used more and more in the sense of today’s Hindi.
(Source: Chapter “The Progress of Hindi, Part 2“, in Literary Cultures in History – Reconstructions from South Asia”)