Because this umbrella is another example of the principle that even the best designed things often fail on the tiniest little detail!
This detail is the velcro on the strip that encloses the canopy into a neat 'pole' when the brolly is closed. The manufacturer really could have spent 5p more on a snap closure which would hold the strip closed forever. I've had brollies with velcro and thus know that the velcro always eventually fails the more the brolly is used over time. And when the velcro fails, the canopy won't be kept tightly closed and that makes the brolly less practical in situations when it would be practical to have it tightly closed.
