Dividends are actually the same as selling a piece of your investment.
The moment dividends are paid the share price falls by exactly the amount of dividend paid. One way to think is that the second before the dividends are paid everybody included the dividend in the valuation of the share price. They expect the dividend to be paid to them. One second after the dividend was paid they no longer include it in the valuation making the share price worth less to them exactly by the amount of dividend paid.
If you had a piggy bank with $100 bill in it and a cookie that is promised to you if you hold the piggy bank with the bill in it at certain time, the piggy bank is worth $100 and a cookie. But once the deadline passes you can no longer get the cookie and the piggy bank converts to being just a regular piggy bank with $100 bill and no cookie promised.
Another way to think is that the company just gave off 1% of their value to shareholders in form of cash making the company 1% poorer.
So if you had a share price of $100 and you expected $1 dividend, the second after the dividend is paid you are left with a share worth $99 and $1 in cash which is exactly what would happen if you just sold 1% of your shares.
And because nobody is surprised by the dividend, the fact of paying it has already been included in the valuation well in advance of payment. There is no reason for the valuation to change due to payment of the dividend (other than the company losing exactly the value they paid in dividend).
So, to summarise:
>> Traditional investments have ways of generating and returning money without selling the asset itself
This is false, as shown by my above explanation. Dividends are not generating anything and are actually the same as selling portion of your asset.