Biblical Hebrew has no vowel markings (well it does, but they are an interpretation), so it cannot be used in daily speech. Modern Hebrew is distinct from Biblical Hebrew. Sanskrit itself does not have much use as an actual language because it lacks a lot of the features that, say, Hindi or English or Ancient Greek have, it has 7 past tenses that are basically identical and it does not make fine distinctions between moods, which it does not have enough of. Only Vedic Sanskrit could actually be used as a language, but similarly to Ancient Greek there are relatively few extant texts in Vedic Sanskrit and certainly the task of learning the language to fluency would be monstrous compared to studying a living language; and one that few, if any, would be willing to devote their life towards, especially considering that Classical Sanskrit already works fine enough as a literary language and is only so practical for that purpose because it has such a strictly defined grammar.