Why is it necessary to warm up an IP?

The whole purpose of using a dedicated IP is to build your emailing reputation in a secluded manner. However, If there is one thing that would spoil the IP reputation if ESPs start receiving sudden bursts of mails from an IP with no emailing history.
If an ESP starts receiving emails from a previously unknown IP, their default stance is to assume that the emails are suspicious, which would impact delivery & inbox placement.

Hence it is essential to gradually increase the volume through your new IP until you are confident that you have built a reasonable reputation to start sending a larger volume of emails.

Please follow below daily chart to warmup your IPs