Good points!

I think it's important to differentiate investing in Steem aka buying and powering-up/staking of Steem.

The latter is needed if a person wants to be able to earn passive vesting-inflation, as well as being able to participate in the voting-game, which includes earning of curation rewards. Last but not least, staking is also necessary to participate in the witness-selection/blockchain governance. All of this requires the participant to accept a 13 weeks powerdown timeframe.

Now, the 13 weeks powerdown period is only preventing people from investing, who would only buy Steem if they could stake it with a lower powerdown time. However, I'm betting that the majority of people who have a problem with 13 weeks, will have a problem with 8 weeks, 4 weeks or even 2 weeks.

It's also important to note, that a certain powerdown timeframe requirement is good and necessary. Voting for witnesses for example, should be for those who have skin in the game and not just for exchanges that are using their customers funds to vote (which is happening on EOS). But also from a security perspective, having your "investment" being locked away for 13 weeks (while only 1/13 is available each week) is a great security bonus. Now, I obviously get that this is not for everyone, most people don't have a huge chunk of Steem in their wallet. Which brings me to the point I was making all-along within this subject:

Dynamic Staking Pools & Powerdown Periods

Look, if you want to stake Steem aka power it up and be able to power it down within 3 days, you should be able to do that, but with restrictions. For example you would only earn a fraction of the passive inflation. You wouldn't be able to vote for witnesses or the SPS. And you wouldn't be able to vote for content.

All of these different Steem espects could have their own minimum required staking period. For example: the passive inflation would grow depending on the locked up period of the user. (1 week = 0.1%, 3 years: 5% ~rough example) or voting for witnesses could require a powerdown period of 8 weeks. Voting for content could require a powerdown period of 2 weeks and the earned rewards could require a powerdown of 1 month, to reduce sell-pressure.

I obviously get the point about making Steem not too complicated, but this is the job of interfaces like Steemit.com, Steempeak, Esteem, etc.

If the question is: what is preventing investors for investing in Steem? and what can we improve to change that for the positive?, then the answer isn't just: let's reduce the powerdown period to 4 weeks. Sorry, but the answer to that is far more complex and will most likely require some kind of dynamic system which isn't enforcing one time/rule for everyone.