Why are size and complexity limited in organisms with colonial or filamentous growth forms?

Size and complexity are limited in systems usually by a combination of factors. Such as access to resources. Successful reproduction. Evolution over time dictates what is a successful balance in size and complexity in a system in its environment. If the resources are there and there is successful adaptation to the environment, systems can be supported that are extremely complex and also huge in size. Say the human body as a system.