Bonds are interesting and you've come across most of what makes them so interesting. The interesting thing with bonds, is all the already outstanding notes of similar remaining duration and underwriting risk are revalued to the newest yields. The "why" will shake out like every single other investment decision. Does this make sense for my portfolio?
I'm sure you know this part but I'll start at the beginning. A bond is a note that says, for $1,000 of your money today I will pay you $1,010 a year from today. The bond issue might be for $1,000,000; so there are 1,000 of these notes. Lets say that they raise the million they are looking for, 1,000 people show up with $1,000 each. Everyone gets a 1% yield; $10 return on $1,000. But lets say that at auction two only $990,000 shows up. These auction two notes are bought for $990 each, they'll all still pay $1,010 after a year, these have a yield of 2%.
If all the holders of auction one hold their notes to maturity, they still realize the 1% yield that was acceptable for their money at the time they bought. But if someone wants to get out of their auction 1 note, they'll have to sell it at the now current yield of 2%, thus taking a loss. Who would buy your auction one note for $1,000 when they could get someone's auction two note for $990. This effect cascades through the varying time-frames and yields. A 30 year note with one year remaining will be priced to a yield of the other one year notes, not the 30 year notes.
Whoever buys the note at the time of issue has decided, x% return on my money is acceptable for that given time frame. Increasing or decreasing interest rate environment doesn't matter. At the time of issue at auction one, 1% was enough given the facts and circumstances.
SHOULD you buy whatever bond if there's a strong possibility we're in an increasing interest rate environment? That depends on your investment horizon. Ideally, when you buy a bond, you are committing that money FOR THAT TIME PERIOD. If rates raise and the value of your bond drops, it doesn't matter to you because your bond will still pay you your agreed upon yield at the time of maturity.
So, who is buying 30 year government bonds? Someone with a lot of money that wants to guarantee a x% return over that time period. Should YOU buy 30 year treasuries? That depends... do you have a 30 year horizon over which you'd like to lock x%?
As to the indicators of recession, you should structure your assets based on what your best understanding of the market. But you should never buy an asset with a longer time frame than your investment horizon.