Here are some of the things you won't find out from the smiling host with the perfect teeth and soap star good looks about the project that got you all fired up on that last show and made you want to try it for yourself. You have to think about it and it will make sense.
First off think about the fact that they are spending 30 to 60 minutes polishing and selling you a project that they claim you can do in a weekend. Adjust that for commercial time and allow for the witty banter between host/homeowner/crew and you get a better idea of the actual time dedicated to giving you the knowledge and information to successfully tackle the job yourself. Make no mistake they ARE selling you the project because the project actually being attempted is what is selling the products. Product manufacturers are not willing to spend big money on advertising that has little chance of benefiting them. thus the main objective of the show after you sort out all the fluff is to sell product.
A good example even if it is rather generic is everyone uses household cleaners and mops and such but the won't sell many of them to the guys watching the basketball game so that's not where their advertising budget will be spent. They will however sell them to the people who couldn't stand another ballgame and decided to go shopping till it was over and these people got their product ideas planted during a nauseating episode of Kardashian something or dancing with washed up has beens. The basketball game sold advertising to the people who make a snazzy bottle of goop that when you wash with it will cause beautiful women to be irresistibly attracted to you.
OK I hope I have cleared up the primary motivation of all the major players here but understand there is a whole set of secondary concerns which is why it is so complicated and takes an entire production company to handle. You must be entertained or you will not watch and will not ultimately buy. This is why the DIY/actors/salesmen are charming, witty and attractive. Also there is genuine interest in your ultimate success since that ups the likelihood of you being a return customer. To this end they employ real tradesmen and fill a good portion of the 30-60 minutes allotted (minus the aforementioned advertising and mugging for the camera) with good honest tradecraft and tips. Based on the level of your experience and the time you actually have to dedicate to the project the timeline indicated to you is more than likely pure fiction. Remember when you take on this project you are taking on the work of an entire team of professionals in addition to execution there will be planning/design. shopping and stocking and a lot of the ugly stuff that doesn't make it to TV like cleaning and prep. I'm not trying to scare you off I want you to get it done and have the satisfaction of a job well done, understanding the true nature, cost and effort you are putting into the project before you begin can make the difference between a nightmare you will regret and a thing of beauty you will be proud to tell people "I did it myself!".