Just flicking through the New Atlas and glanced at some of the comments regarding production of sporophytes in some species. As recorders don't always make a note of whether a species was fruiting or not, it seems the BRC bryophyte database has very few records of fruiting in some very common species, which can then be interpreted as some species producing fruits only rarely. Many of the common dioicous pleurocarps such as Calliergonella cuspidata, Rhytidiadelphus squarrosus, R. triquetrus, Hylocomium splendens, Pseudoscleropodium purum and the like are often reported in the text books as fruiting only rarely. This may be true taking Britain as a whole, but we have found in south Wales that some of these species seem to fruit reasonably often. I usually make a special search for fruits if I come across large patches of pleurocarps and it is surprising how often they are present - late winter seems to be a good time to look. The next time you are walking across a dull bit of heathland with abundant Pleurozium keep an eye open for fruits - although this moss does seem fruit less often than some of the other species mentioned above. You may have to dig around a bit in patches of some species - e.g. in Breutelia setae are very short and fruits hidden well inside hummocks; on Pseudocleropodium fruits appear to be produced on the previous years growth and so despite having a long seta the capsules can still be hidden amongst stems.
I have still to find fruits on Climacium in Wales (seen them once in Yorkshire) and the only time I have seen them on Rhodobryum was when I examined an old herbarium packet containing a specimen collected near Carmarthen, but I live in hope.