Loose, tight, misaligned sockets,
silly socket safety shutters that never work properly, or are just plain fkt by improper usage or design (usually the former PLUS latter)
bent plug pins,
corroded or tarnished contacts
cheap crappy
-Made In Chynna Allleyways- powerstrips/boards
all contribute to DIY fireworks that isn't doing your equipment any favors
Might even blow an internal fuse or trip a sensitive circuit breaker or RCD/GFCI etc
Not worth the hassle or drama stressing your electronics every time you plug in and gamble it will work 'like last time'
get a switch into the equation ASAP