There's a reason no one makes even a 24-200mm FF lens. Several, in fact.
- The main one is that not many photographers who know what they are doing would ever consider buying such a lens for a FF camera, particularly for one with as high resolution as most FF cameras offer in 2021.
- To get anywhere approaching a constant, usable aperture the lens would be very heavy and large.
- Such a lens would be very expensive to produce at any level of decent image quality.
- Lenses with smaller zoom ratios can be smaller, lighter, cheaper, faster, and produce higher image quality than a larger, heavier, more expensive, slower lens with inferior image quality.
The entire point of an interchangeable lens system camera is to allow you to use different lenses that are better or even great at one thing but unsuitable for other things. Fixed lens cameras force you to use a single lens that is mediocre or worse at a lot of things but better at nothing. Insisting on using a single lens for everything on an interchangeable lens camera is not much different than using a fixed lens camera. In some cases the fixed lens camera may meet your needs better than an ILC with only one lens.
The best lenses are all prime lenses. That means a single focal length. No.Zoom.At.All. They're really good when they provide the field of view and other characteristics you need. This is because they can be optimized to do one thing at one focal length. A good flat field 100mm macro lens is different from a good 85mm, 105mm, or 135mm portrait lens. But lenses optimized for doing one thing very well are usually not very flexible, so you need a lot of them for various different things. Some are pretty good for not much money (e.g. EF 50mm f/1.8 STM @ $120). Others are incredibly good for a boatload of cash (e.g. EF 400mm f/2.8 L IS II @ $10K). Most fall somewhere in between.
Compared to their zoom lens counterparts, in addition to equal or better optical quality at a lower price prime lenses can also be smaller/lighter, have wider maximum apertures, and often still be much cheaper than zoom lenses in the same focal length range.
Short ratio zoom lenses, that is zoom lenses with a less than 3X difference between their longest and shortest focal length, can also be very good. But the best ones cost a lot.
When you move outside of the 3x limit is when image quality really starts to noticeably go down. Some 4-5X zoom lenses that fall entirely in the telephoto range can be pretty good. But when you start trying to design a lens that goes from wide angle to telephoto and covers a 5X-10X or more zoom range, that is when it really starts getting difficult to keep it affordable and manageable with regard to size and weight and still provide excellent image quality. You'll usually get better image quality and spend less buying something like an 18-55mm and a 55-250mm pair of zoom lenses than you would get with an 18-200mm 'all-in-one'.
I want to buy a zoom lens for a DSLR but I want its Focal length to start from a small number (18, 55, 100, 200) and end to a very large number (1300, 2600) so it can see near and far. Also I want it to be small to carry it with me.
No such lens is currently available for any DSLR.
The reason there are no such lenses are that they would be far too heavy, much too large, and way too expensive to be practical while still delivering much poorer optical image quality than much smaller, lighter, and cheaper lenses can deliver.
If you really want to go there, you can get a broadcast quality video lens such as the Canon DigiSuper 100AF that projects an image circle large enough for a 2/3" broadcast camera with a 9.3-930mm focal length. It gives an equivalent field of view on such a cameras as that of a 36-3656mm lens on a FF camera. It only weighs 60 pounds and costs a bit more than $200,000. And that is for a 9.59x5.39mm video sensor with a 3.9X crop factor.
For a Full Frame sensor it would need the front element to be 4X as wide, 4X as tall, and be 4X as long. It'd probably weigh about 64X as much (Each lens element would have 64X the volume when 4X larger in the three linear dimensions), and maybe 4,096X as much (i.e. $819 Million USD). If you're asking for the Defense Department of a major industrial power, they might be willing to make one for you?