It's up to us urban gardeners to step into the breach. I've planted nectar-rich single-petalled plants - light purple Buddleia Lochinch (butterflies won't come to dark or white buddleias, so no Black Knight), valerian, thyme, aubretia, cosmos, pale sedums (not Autumn Joy-Herbstfreude, no insect cares for that), asters, Verbena bonariensis ... When the sun is out I chop fruit into a hanging dish, add fruit juice and site it near the buddleia. Caterpillars need food too. I've got a small dedicated border with wild flowers, native grasses and nettles for them.