Earlier quoted context omitted.
That t is not entirely useless (non-native Russian speaker here). Even the pronunciation of 'check' has a starting t sound in it: tʃɛk. Without the starting t, you might end up with something that could be spelled sheck in English. So I'd argue, that the t in transliterations helps people who don't speak Russian to get the ч sound right. Since the transliteration as 'ch' is ambiguous and doesn't appear to work for ma…
(Native Russian speaker here) I don’t really agree. The “t” and “ch” require very different tongue and jaw positions and combining them is awkward and would require a vowel in between when used in a real word. English speakers are perfectly capable of pronouncing ch vs sh (e.g. chair vs share) whereas sh vs sh’ (ш/щ) might be more challenging.
Especially since there exist words in russian language that actually have "т" before "ч", and the sound it makes is different. Compare "отчёт" and "очки" (the closest similar word i could think of by the sound of the first half of it). If you try pronouncing the first word as if "т" wasn't there (or the second word, but as it "т" was there), it will sound both very different and wrong.