Aircraft Mechanic reported upon inspection; a widespread problem of AMM non-compliance to tape joints for fire suppression on several aircraft cargo compartments.

Narrative

On Date I was working a transit check on Aircraft X. I was doing the inspection of the cargo compartment and found that all the tape was missing from the joint between the sidewall panel and the ceiling panels. Both the forward and aft cargo compartments were missing the tape. The AMM (Aircraft Maintenance Manual) specifies that the joints require sealing tape for fire suppression. This has been an issue lately I have been finding. I found this on Aircraft Y on Date1 and Aircraft Z on Date2. There was another aircraft or two but I can not recall the nose numbers. I at first thought this was a one off situation but it appears to be more widespread of an issue. Some have just the ceiling joint but others have been missing sidewall seam tape also. This makes the aircraft not in compliance with the manual and a possible fire suppression issue as the compartment is not sealed.Possibly coming out of heavier checks incomplete as many of the compartments appear to have been redone in new tape and new panels. Much of the compartment is done and repaired but the ceiling seam is consistently missing.