The easy part is "why vote" : The right to vote in a democratic process is a hard won liberty and the envy of many countries around the globe. People die for the right to vote, even if sometimes "none of the above" is our reaction to the inane antics of politicians. The second part is less clear!

Manifesto pledges are as solid as fog. One looks at general tenor of argument and direction, and then accepts that they are surprisingly fallible - stupid decisions are no respecter of political belief or original intention. The reality of our world in the UK is that we are buffeted by forces outside our narrow political environment and a "pledge" will be rapidly eviscerated on the altar of international developments. Terminology is invented to hide the truth or flatter the listener, rarely does it reflect the reality of the proposed action.

Equally, every decision made by political leaders can be heavily criticised with the benefit of hindsight (though I remain perplexed by the decision by one GB to sell gold at the strike price he did). My view is that one takes the broad direction and emphasis as the way to choose; but like all when we are really honest, I admit to being at least a little selfish for me and my family when voting!

(P.S. Feeling especially cynical this week :) )

One further point was made in terms of economic management.
Where is the investment that should have accrued from North Sea Oil?

The majority of what was sold constituted a money pit whilst in public hands. Politics got in the way of active management and necessary investment was hard to justify.
Personally, I think that the privatisation (and later sale) of the building societies by Boards and members was much more malign.
Performance of most of the privatised industries has been much better since their sale.
Keeping them and making them perform better in the public sector might have been a better trick, but not one that governments have been good at.

Well, 'sold' is a word for it; at the time, most thought GB had virtually given it away.

Not really true. Massive nationalisation of the banks with sales of other assets to help pay for the nationalisation and massive borrowings.
And much though our politicians can be blamed for the insufficient regulation etc, the same problems were there throughout the developed world. And rather than simply having cuts there was also QE; unlike the EU.

Again untrue. Offered the opportunity for Brexit, but it was voters who decided to go for it - all political parties, apart form UKIP, were against.

Sharp fall in the pound - true, but only partly because the £ is still higher than it was in the financial crisis.
Foreigners buying our companies at a discount - well no. Companies have often been sold to foreigners and there is only a discount if you think the £ should be higher. If you think it should be lower, and that the UK's future is grim, then we're stealing money from them.
And not many companies have changed hands (yet). And how many of those that have been sold are able to export jobs? ARM? It's mostly IP companies that have gone, not a lot of jobs to go to cheap wage areas.

Advise him not to. That means he can blame all the dumb voters for anything the government does that he doesn't like, like his friends do.

The advice so far is-
Register to vote, i.e "to-day" which is the last day.
Then at least you have the option of voting, should you decide to vote.

Purely out of interest, how many companies since the Brexit vote and the subsequent fall in sterling have fallen into foreign hands a d how many jobs have been transferred?