malays have the strongest fetish of their national flag, i have ever seen. every single flat (or even a shelter in orang asli village) has a need to raise one and you can unconsciously learn every detail (e.g. whether it has the same number of stripes as US flag) after a single day in the country. on the contrary, having spent over a month in singapore, i still had to do a quick check before writing this post what are the colours of the respective singaporan symbol.uniting symbols are probably more important in a federal (and multinational) country, so there might be some government involvement in spreading them in malaysia, although to my knowledge there are none. singapore, however, bans any public display of foreign flags. so, as they say, you better leave your red crossed shirt at home even in the unlikely event that english squad plays in the singaporan stadium.
also, the asymmetry of flag popularity has nothing to do with the love of the country, given the brain drain from malaysia to singapore. so, maybe it's simply an equilibrium of a collusive game in which many flags produce a beautiful harmony, so although your deviation is possible, contributing to turning your city (and maybe your dull building to begin with) more colourful comes at a little cost. still since 'no flags' is another obvious equilibrium, this doesn't answer how they got into the one with 'many flags' in the first place.