If you ever tried to get sheet music for a particular tango, you will have noticed a big gap compared to other genres. Tangos were not in the spot of music publishers for many decades. After WWII tango was considered old-fashioned: They didn't use the (electronic) instruments popular for at young generation, and organizations as the International Council of Ballroom Dancing which defined a social dance inspired by paso doble or a Spanish bullfight and not referring to the original La Plata Tango with it's improvising character and own deep roots and rich history.
During the 1980ies and later, the tango Show Tango Argentino which toured through the US and Europe, demonstrated a high level dancing style, unknown to the ordinary audience. Astor Piazzolla, ignored and rejected at home, escaped to Europe were he matured during many years in Italy. The New Tango was a revelation in Europe, catching open minded jazz lovers and the youth as well.
It was the ignition for the Tango Nuevo, and the tango of the 40ties,
for the dancers, a phenomenon which is still
lasting, from Zurich to Paris, Berlin. New York, Tokyo and Johannesburg.
As a consequence the increasing demand for original tango sheet music
motivated a few music publishers to make some tries.
Indeed, the situation improved a lot. In the past the original tangos were published in a basic version for piano. Sometimes the melody line for violin or voice was added. This explains why there are almost no pieces for bandoneon out there.
Complete arrangements were seldom. The orchestras were forced to arrange themselfs. Of course, the arrranger gave the characteristic style. With some experience you will recognize the arranger of a particular piece. It is very hard to find original written arrangements, if you do, most probably someone wrote it down just by ear. Not everybody is able or willing to write owqn arrangements from scratch. Consider hireing an arrangement service