This thirty second video taken by someone cycling past the Life and Mind building in Oxford nicely illustrates why dropped kerbs are essential for access to off-road cycle parking.
This shows two of the major problems created by not having dropped kerbs to access off-road cycle parking: 1) someone stopping on the carriageway to lift their bike up the kerb, creating a hazard for other people cycling; and 2) someone else using a distant dropped kerb and then cycling for fifty metres or more on the footway in order to get to the cycle parking, creating potential conflicts with pedestrians.
The third major problem is an equity and inclusivity problem that is not illustrated here and is by its very nature never visible. Some people - older people with heavy e-bikes, people with cargo cycles or tandems or tricycles, etc. - may not be able to lift their cycles up a kerb at all. It is hardly feasible, for example, for someone transporting children to stop on a busy carriageway, dismount the children, and then lift their cycle up the kerb. So if cycle parking has no dropped kerbs at all, even at a distance, it will exclude some users completely.