And my changing tastes.
The Register has produced a list of the 'top 10 arcade games of all time'. While I recognise and remember playing happily the first few, everything from 'Outrun' onward never caught my imagination or drew me in. Maybe it was because they were so generic (and heralded the early 1st person shooters, like Wolfenstein) but maybe also it was because I was married by then and 'had a life'.
There's a couple missing too:
Firebird Phoenix (IIRC) was highly addictive and a stage on from Space invaders and Galaxian.
Vanguard was another that we spent many happy hours feeding 10p pieces into.
Finally, whatever happened to Asteroids - a contemporary of Space Invaders, and one that saw at least as much play.