What are the reason why the …

The banks might not be willing to lend certain borrowers  for the following reasons:

1. Banks require proper documents and collateral as security against loans. A number of borrowers have no collateral to pledge against loans, particularly small farmers requiring crop loans. 
2.  Repayment of such a loan is crucially dependent on the income from selling the crop. Since there is a risk involved (in case the crop yield is inadequate for any reason), banks are not willing to lend to such borrowers who cannot pledge collateral which can be sold to recover the loan amount in case of default in paying the loan amount.
3.  The borrowers who have not repaid previous loans, the banks might not be willing to lend them further.
4.  The banks might not be willing to lend those entrepreneurs who are going to invest in the business with high risks.