In her book, Teaching Academic ESL Writing, Eli Hinkel arguest that teachers of English for academic purposes (EAP) often overemphasise the use of connectives, such as however in writing classes.
In fact, I think many writing teachers do spend some time talking about "linking words and expressions". This is a problem, according to Hinkel, because such expressions are actually relatively unusual in academic writing. On p. 293 she gets specific and, citing the Longman Grammar of Spoken and Written English, claims that however occurs at a rate of only 0.10% per million words (i.e., 1 per 100 million words) in academic text. This would be rather upsetting to many writing teachers if it were true.
Fortunately, Hinkel is simply wrong. In LGSWE on p. 887, there is a figure entitled, "most common linking adverbials in conversation and academic prose; occurrences per million words" which has however at a rate of over 1,100 times per million words in academic text. When I pointed this out to her, Hinkel refered me to a figure on p. 562, but this also contradicts her claims. According to a note on p. 561, it includes only those adverbs occurring at least 200 times per million words, and the legend shows that the mark beside however means "occurring over 1,000 times per million words". In fact, a quick check of the BNC academic sub-corpus (using VIEW) has however at 1,216.62 occurrences per million words, making it the 68th most common token in that section of the corpus. This is many orders of magnitude larger than Hinkel's claim of 0.10% per million words and stands in striking contrast to her assertion that "sentence transitions are actually not common at all."
When I pointed this out to her, her response was merely, "Biber's table could be more specific."