I see that there are some ICO who collect ETH without smart contract and would like to know the negatives and positives for such decision.
Some projects use per participant Ethereum adderesses to collect funds, in a similar fashion one would do with Bitcoin fund collection. This is usually because the team lacks necessary experience to deal with smart contracts.
The downside of this approach includes the lack of transparency and the lack of accountability that follows.
Using a smart contract, with a published open source code that is preferably verified on EtherScan.io or similar service, allows anyone to verify that
The amount of funds collected are correct and there are no false claims about excessive raises to create hype around the project
Tokens are correctly distributed and there is no under the table deals to give preferable treatment to some parties
Also as stated above if the team cannot build or have someone to build smart contracts for them, it usually demonstrates lack of technical understanding, which is a requirement to execute a successful blockchain based technology projects
Public smart contract token sale code, in a principle, enables more democratic investments and gives more investor protection.
Maybe some companies are not using smart contracts for their crowdsale simply because smart contracts are not allowing dynamic pricing and they (the company) would like to offer the contributor an option to decide when to enter the market.
Locking the crowdsale price doesn't really give you the option to choose when the time is right for you, right? As it doesn't matter when you jump on the train...