As I understand it, GnuPG allows the creation of multiple subkeys, but multiple encryption subkeys are problematic because it's not clear which encryption subkey someone should use when sending a message. As such, by default, when a person sends a message to you, their software will select the most recent encryption subkey. This limits the utility of having multiple encryption subkeys on different devices, but not necessarily signing subkeys.
Now, imagine a situation where we have two laptops. Neither laptop contains the master key, but only a single subkey for signing (S) and subkey for encryption (E). Since we have trouble using multiple encryption subkeys, we have a setup like this:
Laptop 1: E, S1 Laptop 2: E, S2
Hence, each laptop has its own signing subkey, but they each share an encryption subkey. Now, say we lose laptop 1. At this point, using the master key, we can revoke the certificate for E and S1. Since the master key was safe, we preserve our WoT. However, since E is no longer valid, we still need to update laptop 2 with a new encryption subkey. Since we always need to update laptop 2 in the case that laptop 1 is compromised, why should we prefer the setup above to a key setup
Laptop 1: E, S Laptop 2: E, S
Certainly, if we're only signing, having separate signing subkeys for each device makes sense. However, if we need to sign and encrypt, does it still make sense to have separate signing subkeys for each device?
Following up on @jens-erat's answer, I checked and GnuPG does allow us to specify exactly which subkey we use for encryption. Simply, append ! after the specified key. This forces GnuPG to use this particular key and not go through the normal calculation as to what key to use. This is in the man file under the section "HOW TO SPECIFY A USER ID" under subheading "By key Id." Then, as @jens-erat stated, we could add a bunch of notations to the key, which specify which key should be used for which situation or address. By looking at the notation block with --list-sigs and then specifying the exact key with !, we can utilize multiple encrypting subkeys. That being said, I don't think this is standard use and will likely cause use problems for people.