Your question is quite valid. Those who hire must make arrangement to organise job interviews on Saturdays if not on Sundays. However, only first line interview can be held on Saturday or Sunday. Functional managers or HODs or still senior manager may not spare their time for the interviews on weekend unless special circumstances demand it.
To solve this problem, the job candidate may take leave and appear for interview.
Good query. However, for those companies that are 5 days working, the concerned HR would want to enjoy his/her deserved weekend rather than showing up at work. I know it is hard for any candidate to attend an interview on weekday but that is the test of his/her level of interest for that interview. Best option is to take half day on any weekday rather than taking full day leave for interview.
Thanks and Regards,