I completely agree about powering up - but these are not really valid reasons.

Accounts with 500STEEM POWER or more make up only 1% of all STEEM wallets. If you power up to 500 or more STEEM POWER, it will put you in the top 1% of STEEM POWER holders.
I guess this is probably a motivation for some - but it just shows how little we value our platform - and that the distribution of stake is pretty much delta function. :)

If only 300,000 people held 1000 STEEM POWER each, under the current supply, there would be almost no liquid STEEM available. Having 500 STEEM POWER puts you half way there. (Ifs and weres - have no argument against it- but I guess everyone is waiting to sell steem as soon as the price jumps) - which is okay :)

Becoming a minnow gives you a voting slider on Steemit.com. - there is just too many effort letting people know that there are other platforms than steemit, and most of them have built in slider independent of Steem power.

Becoming a minnow is a personal achievement and milestone for many. ===

Powering up increases the value of your vote. - true that

Powering up increases the stake you hold in witness voting. - :) distribution, distribution.

Locking liquid STEEM into STEEM Power makes STEEM a scarcer resource and in turn should help the price as long (as there is demand.)
Powering up shows other STEEM users that you have long term intent and confidence in STEEM
Powering up gives the STEEM ecosystem time to grow and flourish. Remember, STEEM is rather new in the general terms of things.
Powering up is investing in your future.
Part of the newly created STEEM each day is shared with STEEM Power Holders. Powering up STEEM now will return you with more STEEM in the future.

Once again - this is not an attempt to persuade people not to power up ) but just some thoughts on the things you pointed.

Cheers, and power up! :) I know I will :)