Dear Ramesh,
The grace period is an extended period granted as a special favour. An employee may start from home at a fixed time, but sometimes, contingencies may arise because of traffic bottlenecks or something else. To provide cover for such a one-off event, a grace period is given.
While reporting for the duties, whether to grant this special favour or not is the employer's prerogative. If the employer withdraws it, then the employees cannot question it.
Unfortunately, some employees misuse the facility of grace time perennially. If you check the employees' punching records, then you might observe that a few employees avail of the facility of the grace time with the utmost regularity. Suppose on average, the employee reports late for duties by five minutes. But if he/she does it 120 times, the total late-coming works out to 600 minutes. That is as good as one man-day. Is this not the organisation's big loss? This calculation is just for one employee. If the loss is calculated for all the employees, then the cumulative loss could be far greater.
Thanks,
Dinesh Divekar