This was in response to the growing popularity of the hippie subculture worldwide; the government deemed such an influence to be negative and detrimental to the country's development.
Among others, the Bee Gees, Kitarō, and Led Zeppelin all were forced to cancel their gigs in Singapore because they refused to accommodate the policy.
Prime Minister of Singapore Lee Kuan Yew even had to cancel a business trip owing to heavy protests by a few individuals affected by the ban.
[1] The Singapore Government claimed that so-called hippies were negative influences for Singaporeans capable of "corrupting" their minds and "polluting" the country's society.
[a] In the first few years after the policy's introduction, the consequences for not abiding by it were already intrusive: long-haired males spotted by the police were forced to cut it short.
The Australian High Commission took note of their dissatisfaction, and promptly made a formal inquiry into the incident, though admitting that it was not its prerogative to complain about it.
[1] Although the ban by right only applied to men, a handful of female schoolchildren in Singapore were reported to have had their long hair forcefully cut short after being warned countless times.
[7][8] Similarly, Cliff Richard, Led Zeppelin and the Bee Gees were all supposed to perform in Singapore at different points in time but left because of the ban.