This happens primarily due to substandard workmanship. Sometimes this problem occurs even after few years. Generally surface of windows are smoother, therefore bonding with masonry gets gradually detached. There are many sealants and chemicals are now available in the market which can seal these gaps to prevent water seapage.
Each state has different development control rules and as such the conversion of agrictural land to commercial/ industrial user would depend on such State laws. At time such laws are relevant as in sum cases agricultural lands are not being used for agricultural purposes for several reasons.