If you want the multiple ISPs to work as backups to each other, yes.
Say you have two different ISPs, A and B, to connect to and get two different IP networks from each. If you want the ISP A to route the IP network you got from the ISP B to you, and vice versa, which is what you usually want for the enterprise network, then you need BGP because you have to advertise both of the IP addresses through A and B. Otherwise, the ISP A won't advertise the IP addresses from the ISP B for you.
So, when you have a portable address range(as Zac67♦ said) or multiple different address ranges belong to different entities, you need BGP, because ISPs won't advertise the IP address ranges that don't belong to them. And many ISPs don't accept the IP ranges they didn't assign or made a business deal for. This way, no entities advertise the IP address spaces that don't belong to them, hopefully. (I heard that some ISPs don't manage these IP advertisements they accept.) This is more of a policy thing than a technicality.
However, if you just want to use them separately and not to advertise both of the IP addresses to both ISPs, then you're fine without BGP.