My understanding is that for centuries after Bach's death, they were disregarded. They were seen almost as etudes, for cellists to use for practice to hone their technique. They didn't really gain their current status as respectable concert pieces until Pablo Casals dug them up in the early 20th century and produced his classic recordings.
Not exactly.
Bach died in 1750. At this time the "market" for music was going through big changes. In Bach's time the main customers for music were courts of barons and kings and municipalities. That's the career he had, a musikmeister.
But look deeper and you'll see an economic landscape changing: the rise of cities, merchants, financial capitalism, etc. A bourgeoisie was rising and consuming music in concert rooms, opera houses and for private playing. But this bourgeoisie had different tastes. They didn't have a deep musical instruction so they preferred more "pop" music: easy to listen, easy to play, easy to follow. Bach's music is the opposite of it. It was out of fashion.
Bach's sons followed this simplified style. Most of all, Carl Philip Emanuel Bach was big into it. He got so good at this that he became an instructor and mentor to both Mozart and Haydn.
But Carl never stopped adoring his father music and used Johan Sebastian Bach (his dad) material for teaching. So J.S. Bach was widely known and venerated among musicians, including Beethoven.
However, the public recognition of Bach's worth only began when Mendelssohn made public presentations of his masses, in 1829. But this was 37 years before Pablo Casals was born.
The initial obscurity of the cello suites was part of the larger disregarding of Bach's work, in the shift from baroque to classical style. But did the "re-"regarding of the cello suites happen at the same time as Mendelssohn? Or did Mendelssohn only start the process, by rediscovering a few good pieces, while other pieces like the cello suites waited another ~hundred years?
My understanding is that both Mozart and Schubert started to fall out of fashion in the early to mid 1900s for being "lightweight" and just stepping stones to Beethoven. It took some dedicated musicologists from Britain who championed them in the 50s to really solidify their standing in music history.
I also believe we are now seeing a resurgence of interest in Salieri in part thanks to the movie...
The cello wasn't a popular solo instrument. Pablo Casals was a celebrity who made the instrument a much bigger deal. The cello suites rode on his celebrity.
As were the Partitas and Sonatas for unaccompanied violin. It wasn’t until the great 19th century violinist Joachim began playing them in recitals that they came to light again. Even then it was not widely accepted. I believe it may have been George Bernard Shaw who had pretty harsh words to say about the very idea of treating these works seriously. My daughter is preparing for her conservatory auditions; and these works are now compulsory literally everywhere!
Username checks out.
Interestingly, his encores were just to replay a movement of Bach. I mean, after that, what else?