At the beginning, a suit of armour was meant for battle and a knight who fell off his horse should be able to continue fighting. In the 14th and 15th century, one could move around in a suit of armour pretty well; one could even tumble over ones head. More then some stairs were probably not necessary. For jousting, the 16th century smiths developed special suits of armour. These contained for example an extra strong breast plate and a helmet in which the head could not move anymore. Leg protection was abandoned as well. This was worked into the saddle to make mounting the horse easier. So they did not need to use a hoist.