I travel alone and most deals I find are for couples only. Why is it more expensive for single travelers who's tired of finding a person to travel with to get the deal and just want to just enjoy their vacation alone until they find THAT person.
It really depends on the destination. Anywhere where the price of hotels is per room, a single traveler will incur a higher cost. Brazil took it one more level up by having most restaurant meals specified for two! Sometimes I was able to ask for a half-portion which is half of two, so quite enough for one and then I ate fast food pretty often which comes by default in portions for one. Remember that taxis also generally have a per-car price. The second biggest expense after hotels with costs per-unit rather than per-person is car rentals.
You are right that travel deals are often advertised with a per-person cost yet require at least two. This is because spreading shared costs makes the price seem lower but in fact it may not be such a good deal when you add up all the costs for each person.
What you need to do is locate hotels that charge per-person. There are many such places around the world but some destinations do this more often than others. There packages even that let you request a roommate and they will match you with someone who selected the same.
The key to finding a deal is to look and do so often. When cost is really low, there is not much lower they can offer it for two people. Often when I see really low prices for couples, it is for packages that include more services.
Besides the opportunity to split costs, there's a separate effect where it is assumed that a solo traveler is a business traveller, and therefore they can charge more than a family leisure traveller.
Example: I was booked into a double queen room at a Washington DC hotel, and at check in I asked for a single king room, and they wanted an extra $80/night.
Another example is the British rail network's Two Together Railcard. 30% off when two tickets are purchased together, even though two people take up exactly twice as much space on the train. This basically allows them to charge commuters and business travelers 30% more!
You can't do anything about this in many cases, but you certainly can do things like book a hotel room with two beds.