They do not have 'all' features of ICOs but they do have some features, and work well for vanilla ICOs without special rules. Other ICOs can be handled manually or with a script. I've noticed that even with ERC-20, there are many ICOs that use a script to distribute the tokens after ICO rather than having the smart contract do it automatically. This protects against coding errors, unusual circumstances, etc. Of course there are some that do distribute by a smart contract according to complicated rules and those are not currently a good fit for SMT.