Two consecutive letters in a word is not the most useful definition of a bigram in English text. More useful is two consecutive letters in a stream of English text -- paragraphs and all that -- either with or without spaces between the words. Bigrams with spaces are useful to train deep learning artificial neural networks to recognize or produce English text. Bigrams without spaces are useful for the business of cracking ciphers with cryptanalysis, or the pastime of solving cryptograms. For example, if you treat FB is an impossible bigram in solving a cryptogram, then it would be impossible to recover the plaintext ATHIEFBORROWEDMYCAR, as it contains FB. Also, in a world of English-language news and analysis that has been saturated with IRAQIS and AL-QAEDA / AL-QAIDA for decades now, there are certainly other letters that follow Q, even within a word.