Answer by Krishnendu Bhattacharjee:
Sanskrit used to be the language of science and technology in ancient India. However, the knowledge was kept secret, and the language did't belong to all castes. Only brahmins and royalty were to be trusted, and maybe occasionally some very inquisitive and sharp individuals from other castes. The prime example of this can be seen in the Ekalavya episode of Mahabharata.
Since the majority were deprived of the knowledge, it might have been the reason for discontinuance, along with numerous invasions and subsequent dark ages.
Historically till 15th century or so, Latin used to be the official language of the west, and English was the language used by radicals who brought about the changes responsible for the modern technological revolution, which is continuing even now.
Although ancient Indians made many discoveries, they came nowhere close to what we have achieved today as a global civilization. In modern context, many commonly used technical words are just not present in Sanskrit. So, it's easier to use the english words, instead of inventing sanskrit synonyms, which anyone who doesn't know sanskrit won't understand, and eventually to make them understand we have to use english. In that case, why would someone bother using a language which is essentially limited to, maybe not even 0.001% of Indian population?
With technologies like google translate becoming commonplace, language is becoming less of a barrier in communication each passing day.
Although it sounds romantic and nostalgic thinking about why we don't follow our own ancient language, even today, language is being used to create division between human beings, which should not.
As it being a compulsory part of school education, why should it be, when there is no need and use of the language anymore? Does anyone write any literature, or technical in sanskrit anymore? If they do, how many people read them?
I think it gets down to what we think is more important: the knowledge, communicated in any language, or the language itself?
If it's language, literary works are a better way to promote it than technical papers. If it's knowledge, then language is far less important than the idea which needs to be communicated.