A321 Flight Attendant reported multiple jump seats were found during preflight to have loose and/or missing hardware and noted it was common for aircraft with the same type of jump seat to have this issue.

Narrative

During preflight I discovered that the screws and bolts on my jump seat at the 3L door were loose. I then looked at the jump seat at the 2R door to compare and found that the right side hinge was missing the screw and bolt altogether. I checked the front jump seat at the boarding door and found the inboard jump seat was also missing the screw and bolt on the hinge on the right side. I notified the Captain (CA) and he looked at the front jump seat and saw that the screw/bolt was missing and the hinge was coming apart. After notifying the CA I went to look at the 4L door jump seat and found that a screw was missing on the left side hinge. I updated the CA with this information.We departed with the four jump seats in this condition.Suggestions: I have found that on aircraft with this type of jump seat it is very common to find loose or missing bolts. Our earlier flight from ZZZ had a jump seat missing hardware and Maintenance was called to place it out of service. It seems to be a design flaw that is commonly overlooked as is the case in this flight finding 4 jump seats with loose or missing hardware. I don't know how; but someone needs to figure out a way to keep these bolts from loosening up and falling out undetected.Unknown why the CA did not contact Maintenance to evaluate the broken jump seats.