OITL Vs. OILM table

Hi,

For linking Inventory documents like Goods Issue with their batches, we can navigate from:

IGE1 to OITL to ITL1 to OBTN

Or

IGE1 to OILM to ILM1 to OBTN

My question is, what is the difference between OITL and OILM tables?

OILM contains lot more fields than OITL.

Why did SAP introduce 2 identical tables? SAP may as well have introduced the additional fields in OILM in the OITL table itself, or vice versa.

Any insight will be helpful

Thanks.