Even if every man got married to one lady, there would still be more than 30 thousand women in USA who would not be able to get spouses (considering that The united states has twenty-five thousand gays). There would be more than four thousand women in Excellent England, five thousand women in Malaysia and nine thousand women in Russian federation alone who would not be able to discover a spouse.
Suppose my sis happens to be one of the single women residing in USA, or assume your sis happens to be one of the single women in USA. The only two choices staying for her are that she either marries a man who already has a spouse or becomes community residence. There is no other choice. All those who are moderate will opt for the first.
In European community, it is typical for a man to have mistresses and/or several extra-marital matters, in which situation; the lady brings a disgraceful and unsecured lifestyle. The same community, however, cannot agree to a man having more than one spouse, in which women maintain their honorable, sensible place in community and cause a secured lifestyle.
Thus the only two choices before a lady who cannot discover a spouse is to get married to a wedded man or to become community residence. Islam wants providing women the honorable place by allowing the first choice and disallowing the second.
There are several other factors, why Islam has allowed restricted polygyny, but it is mainly to secure the modesty of women.