Is monero completely different from bitcoin in the sense that wallet creators haven't added monero as into their list of supported coins? Monero has a pretty decent big following, but its not support in many of the multi-coin wallets. What is the reason for this?
Monero has a completely different code-base than Bitcoin. It was not inherited from Bitcoin, and it was written from scratch (Bytecoin was the first CryptoNote cryptocurrency, and Monero inherited that codebase, not Bitcoin's - it's a fork of Bytecoin)
Thing is, all Bitcoin clones can simply copy what's already been done and maybe do some small tweaks. On the other hand, people working to implement Monero are pioneers. It doesn't mean that it's harder, but just that it requires work whereas for Bitcoin most of the work has already been done and can be re-used.
Also, due to mechanics of CryptoNote coins, any light-wallet implementation requires more resources on the back-end. Where Bitcoin can simply look-up the balance, Monero has to scan the entire blockchain.